A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • one year ago

Currently have the first 3 answers here to start us off, not sure where to go from here, please help! (problems: http://imgur.com/Eo8fZIR,mJ2vS04,3ys9vme,xyjbOve ) here's what i've got: * A=40 * B=20 * C=12 hour period

  • This Question is Closed
  1. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    What exactly is the question?

  2. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    There's multiple questions, would you like me to type them out for you? I don't mind.

  3. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Are there more than the 3 in the link? Or are you just asking if those answers are correct?

  4. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    There are more than 3, I have the first 3 which I listed and I need assistance with the rest, I believe the answers for the first 3 that I got are vital to answering the rest.

  5. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    There are 5 more questions, 2 bonus questions but i'm not too worried about them.

  6. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok. I didn't see the links to the other questions before

  7. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Oh it's alright, you've got it or do I need to type them?

  8. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I see them.

  9. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    For part d, a is the amplitude and b is 2π divided by the period The y = cos x parent function has a maximum on the y-axis. Your function has the minimum there, so make "a" negative

  10. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so for A, the amplitude was either 40 or 20 from the previous questions, correct?

  11. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    The amplitude is 20, the answer from B

  12. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I didn't have my work pulled up sorry about that, so it's y=20 cos 2pi x?

  13. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Wait! I read you wrong, a=20 and b=2pi/the period?

  14. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    close. you need to divide 2π by the period of 12 and make the amplitude negative to account for the reflection \[y=-20\cos \frac{ 2\pi }{ 12 }x\]

  15. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Am I going to need to get this down to one number for the answer to "a=" or will it be an equation?

  16. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Or will this be for both a= and b=

  17. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    oh you're right. They are asking for a and b separately

  18. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so a will be -20 and b will be π/6

  19. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Does that make sense?

  20. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    That does, I was wondering when the negative 20 would come in as I looked around online and saw that it would turn out like that, now the next question is to "sketch" and label a graph, Seeing as we can't really do that here, what would I put into my graphing calculator to figure this out?

  21. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Not sure if the draw option is any use, im new here

  22. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    We could use this: https://www.desmos.com/calculator

  23. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok

  24. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so you want to enter the equation we found above. and set your window to show 1 period at least

  25. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so your horizontal axis should be from 0 to 12. and vertical from -20 to 20

  26. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    y=-20 cos 2pi/12x is the equation I want to put in?

  27. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Reduce the 2π/12 to π/6 and use parentheses to avoid ambiguity y=-20 cos (pi/6)x

  28. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Hold up, put everything after cos in (). y=-20 cos ((pi/6)x)

  29. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Have this so far, should I fix it with the ()'s? http://imgur.com/ptftpkN

  30. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Yes

  31. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    If I add the extra parenthesis it makes two lines, like this: http://imgur.com/KM6VOZB

  32. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Is that what we want?

  33. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes. If you zoom out you'll see the waves

  34. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Yes! alright so that's all that was? we're done graphing?

  35. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes.

  36. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Mind sticking around and helping with the rest? I'll give you medals or whatever the currency on here is.

  37. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    oh yeah. I just meant we were done with that question

  38. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Alright so F, how do we find the average water levels?

  39. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Just the top of the waves?

  40. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    It's the average of the maximum and minimum, which I think was 32 and 12. I need to go back to the beginning to check

  41. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    52 and 12 I believe

  42. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    you're right

  43. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    So what can we do with those to find the average? Divide?

  44. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Add them and then divide (52+12)/2 = 22

  45. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Crazy how complicated they make it sound and then it's that easy! This next one may be a bit of a challenge

  46. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I have the graph on hand, how do I determine where the times are?

  47. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    That's where the first column comes in. 11:15 is 2 hours after 9:15, so you want to find y when x = 2.

  48. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    will finding y give the water level?

  49. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    correct!

  50. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    not sure how to find it with just x, walk me through it?

  51. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes. It might actually be easier to do this on a calculator than to use the graph. For the first one, plug in 2 for x. y = -20 cos ((π/6)*2) http://www.wolframalpha.com/input/?i=-20+cos+%28%28%CF%80%2F6%29*x%29+at+x+%3D+2

  52. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so for each one we just plug in the hours and we get the level, for this it's -10?

  53. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    right

  54. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    3:45pm is 7 hours, right?

  55. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    6.5 hrs

  56. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    19.31?

  57. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes

  58. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    and then 6:15 is 9 hours? I'm in high school I should really be able to tell time at this point but it's hard without a clock to look at.

  59. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    lol. It is 9. I'm just as pathetic. I have to count it on my fingers

  60. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    wolfram just gave me the answer as "true", that cant be right

  61. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    copy your link here

  62. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    http://www.wolframalpha.com/input/?i=y+%3D+-20+cos+%28%28%CF%80%2F6%29*9%29

  63. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Just take out the y= so it will evaluate the expression

  64. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    0?

  65. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yep

  66. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    for the next one it's looking like we're working backwards, it gives us the water level but not the time, how do we manage this?

  67. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Use 7 for y and solve for x. 7 = -20 cos ((π/6)*x)

  68. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    http://www.wolframalpha.com/input/?i=7+%3D+-20+cos+%28%28%CF%80%2F6%29*x%29?

  69. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    8.5 hours?

  70. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    or 7.5

  71. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    http://www.wolframalpha.com/input/?i=7+%3D+-20+cos+%28%28%CF%80%2F6%29*x%29%2C+0%3Cx%3C12

  72. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    sorry about that. You have to restrict the domain to just the period, or it will give all possilbe answers

  73. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    this is looking like jibberish to me, is it 12? i'm seeing 12 a lot in there

  74. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    hold up. can we go back to part c for a second?

  75. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    the 12 hour period, yes

  76. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    The period is actually 24. (9:15 to 3:15 is only half the period)

  77. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    9:15 to 3:15 is a six hour gap. so six hours from low to high plus 6 hours from high back to low is a 12 hour period, right?

  78. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok. yes. massive brain fart

  79. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so is H a 12 hour period as well?

  80. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes, so there will be two solutions over the 12 hour period

  81. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Ignore all the "alternate form" gibberish and scroll down to where it says "solutions" You may have to click on the "approximate form" box http://www.wolframalpha.com/input/?i=7+%3D+-20+cos+%28%28%CF%80%2F6%29*x%29%2C+0%3Cx%3C12

  82. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Do you see x = 8.32 and x = 3.68?

  83. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I see them now yep, what do they have to do with it?

  84. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    that equals 12?

  85. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    no, they are the x values where the water level is 7

  86. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    and they helped us determine that it's a 12 hour period in some way I guess?

  87. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    The other way around. The equation 7 = -20 cos ((π/6)*x) has infinitely many solutions. We used the 12 hour period to restrict the amount of solutions the equation would give us. That's why the 0<x<12 is in there

  88. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    got it!

  89. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    So to find the times for H, add 3.68 hrs and 8.32 hrs to 9:15.

  90. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    20.115

  91. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    not sure how to add .___ in time

  92. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    9:15 is 9.25 hours 9.25 hrs + 3.68 hrs = 12.93 hr (pm) convert 0.93 hrs to minutes by multiplying by 60 → 55.8 minutes First time 12:56 pm

  93. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    wait a minute are we still on H or have we moved onto the bonus questions? I'm getting lost in all these times here as I know 9am is involved in both

  94. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I thought we were still on H

  95. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    No this is still H

  96. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I was showing you how to add the times.

  97. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    The first time we got for H was 3.68 hours. We need to add that to 9:15 to get the time of day the question is asking for

  98. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    that makes much more sense, and when you did that you got 12.93, correct? should we round this?

  99. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    With 12.93, we have to convert the decimal part to minutes, because there's no 12:93 on a clock. That's why I multiplied 0.93 by 60 to get 55.8, and I rounded that to 56 minutes

  100. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    So it's only a 56 minute period?

  101. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    no

  102. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    12 hours 56 minutes

  103. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    12:56 is the time at which the water level is 7

  104. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    got it now, thanks for the description, it's okay if you dont want to do the bonus questions but if you're up for the challenge I am as well

  105. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    give me a sec.

  106. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    sure

  107. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    If the low tide repeats every 12 hours, there will be 3 in a 24 hour period, inclusive. |dw:1433136689393:dw|

  108. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    and 2 high tides

  109. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    and you can go off that same chart to get both? I'd think so since high and low are both on there

  110. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes you can

  111. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Well I gave you best response which I guess gave medals, is there anything else I can give you? very thankful you stuck around to help

  112. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    No I think that's it :)

  113. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.