anonymous
  • anonymous
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
Algebra
  • Stacey Warren - Expert brainly.com
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SOLVED
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schrodinger
  • schrodinger
I got my questions answered at brainly.com in under 10 minutes. Go to brainly.com now for free help!
anonymous
  • anonymous
What exactly is the question?
anonymous
  • anonymous
There's multiple questions, would you like me to type them out for you? I don't mind.
anonymous
  • anonymous
Are there more than the 3 in the link? Or are you just asking if those answers are correct?

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More answers

anonymous
  • anonymous
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.
anonymous
  • anonymous
There are 5 more questions, 2 bonus questions but i'm not too worried about them.
anonymous
  • anonymous
ok. I didn't see the links to the other questions before
anonymous
  • anonymous
Oh it's alright, you've got it or do I need to type them?
anonymous
  • anonymous
I see them.
anonymous
  • anonymous
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
anonymous
  • anonymous
so for A, the amplitude was either 40 or 20 from the previous questions, correct?
anonymous
  • anonymous
The amplitude is 20, the answer from B
anonymous
  • anonymous
I didn't have my work pulled up sorry about that, so it's y=20 cos 2pi x?
anonymous
  • anonymous
Wait! I read you wrong, a=20 and b=2pi/the period?
anonymous
  • anonymous
close. you need to divide 2π by the period of 12 and make the amplitude negative to account for the reflection \[y=-20\cos \frac{ 2\pi }{ 12 }x\]
anonymous
  • anonymous
Am I going to need to get this down to one number for the answer to "a=" or will it be an equation?
anonymous
  • anonymous
Or will this be for both a= and b=
anonymous
  • anonymous
oh you're right. They are asking for a and b separately
anonymous
  • anonymous
so a will be -20 and b will be π/6
anonymous
  • anonymous
Does that make sense?
anonymous
  • anonymous
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?
anonymous
  • anonymous
Not sure if the draw option is any use, im new here
anonymous
  • anonymous
We could use this: https://www.desmos.com/calculator
anonymous
  • anonymous
ok
anonymous
  • anonymous
so you want to enter the equation we found above. and set your window to show 1 period at least
anonymous
  • anonymous
so your horizontal axis should be from 0 to 12. and vertical from -20 to 20
anonymous
  • anonymous
y=-20 cos 2pi/12x is the equation I want to put in?
anonymous
  • anonymous
Reduce the 2π/12 to π/6 and use parentheses to avoid ambiguity y=-20 cos (pi/6)x
anonymous
  • anonymous
Hold up, put everything after cos in (). y=-20 cos ((pi/6)x)
anonymous
  • anonymous
Have this so far, should I fix it with the ()'s? http://imgur.com/ptftpkN
anonymous
  • anonymous
Yes
anonymous
  • anonymous
If I add the extra parenthesis it makes two lines, like this: http://imgur.com/KM6VOZB
anonymous
  • anonymous
Is that what we want?
anonymous
  • anonymous
yes. If you zoom out you'll see the waves
anonymous
  • anonymous
Yes! alright so that's all that was? we're done graphing?
anonymous
  • anonymous
yes.
anonymous
  • anonymous
Mind sticking around and helping with the rest? I'll give you medals or whatever the currency on here is.
anonymous
  • anonymous
oh yeah. I just meant we were done with that question
anonymous
  • anonymous
Alright so F, how do we find the average water levels?
anonymous
  • anonymous
Just the top of the waves?
anonymous
  • anonymous
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
anonymous
  • anonymous
52 and 12 I believe
anonymous
  • anonymous
you're right
anonymous
  • anonymous
So what can we do with those to find the average? Divide?
anonymous
  • anonymous
Add them and then divide (52+12)/2 = 22
anonymous
  • anonymous
Crazy how complicated they make it sound and then it's that easy! This next one may be a bit of a challenge
anonymous
  • anonymous
I have the graph on hand, how do I determine where the times are?
anonymous
  • anonymous
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.
anonymous
  • anonymous
will finding y give the water level?
anonymous
  • anonymous
correct!
anonymous
  • anonymous
not sure how to find it with just x, walk me through it?
anonymous
  • anonymous
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
anonymous
  • anonymous
so for each one we just plug in the hours and we get the level, for this it's -10?
anonymous
  • anonymous
right
anonymous
  • anonymous
3:45pm is 7 hours, right?
anonymous
  • anonymous
6.5 hrs
anonymous
  • anonymous
19.31?
anonymous
  • anonymous
yes
anonymous
  • anonymous
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.
anonymous
  • anonymous
lol. It is 9. I'm just as pathetic. I have to count it on my fingers
anonymous
  • anonymous
wolfram just gave me the answer as "true", that cant be right
anonymous
  • anonymous
copy your link here
anonymous
  • anonymous
http://www.wolframalpha.com/input/?i=y+%3D+-20+cos+%28%28%CF%80%2F6%29*9%29
anonymous
  • anonymous
Just take out the y= so it will evaluate the expression
anonymous
  • anonymous
0?
anonymous
  • anonymous
yep
anonymous
  • anonymous
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?
anonymous
  • anonymous
Use 7 for y and solve for x. 7 = -20 cos ((π/6)*x)
anonymous
  • anonymous
http://www.wolframalpha.com/input/?i=7+%3D+-20+cos+%28%28%CF%80%2F6%29*x%29?
anonymous
  • anonymous
8.5 hours?
anonymous
  • anonymous
or 7.5
anonymous
  • anonymous
http://www.wolframalpha.com/input/?i=7+%3D+-20+cos+%28%28%CF%80%2F6%29*x%29%2C+0%3Cx%3C12
anonymous
  • anonymous
sorry about that. You have to restrict the domain to just the period, or it will give all possilbe answers
anonymous
  • anonymous
this is looking like jibberish to me, is it 12? i'm seeing 12 a lot in there
anonymous
  • anonymous
hold up. can we go back to part c for a second?
anonymous
  • anonymous
the 12 hour period, yes
anonymous
  • anonymous
The period is actually 24. (9:15 to 3:15 is only half the period)
anonymous
  • anonymous
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?
anonymous
  • anonymous
ok. yes. massive brain fart
anonymous
  • anonymous
so is H a 12 hour period as well?
anonymous
  • anonymous
yes, so there will be two solutions over the 12 hour period
anonymous
  • anonymous
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
anonymous
  • anonymous
Do you see x = 8.32 and x = 3.68?
anonymous
  • anonymous
I see them now yep, what do they have to do with it?
anonymous
  • anonymous
that equals 12?
anonymous
  • anonymous
no, they are the x values where the water level is 7
anonymous
  • anonymous
and they helped us determine that it's a 12 hour period in some way I guess?
anonymous
  • anonymous
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
anonymous
  • anonymous
got it!
anonymous
  • anonymous
So to find the times for H, add 3.68 hrs and 8.32 hrs to 9:15.
anonymous
  • anonymous
20.115
anonymous
  • anonymous
not sure how to add .___ in time
anonymous
  • anonymous
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
anonymous
  • anonymous
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
anonymous
  • anonymous
I thought we were still on H
anonymous
  • anonymous
No this is still H
anonymous
  • anonymous
I was showing you how to add the times.
anonymous
  • anonymous
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
anonymous
  • anonymous
that makes much more sense, and when you did that you got 12.93, correct? should we round this?
anonymous
  • anonymous
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
anonymous
  • anonymous
So it's only a 56 minute period?
anonymous
  • anonymous
no
anonymous
  • anonymous
12 hours 56 minutes
anonymous
  • anonymous
12:56 is the time at which the water level is 7
anonymous
  • anonymous
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
anonymous
  • anonymous
give me a sec.
anonymous
  • anonymous
sure
anonymous
  • anonymous
If the low tide repeats every 12 hours, there will be 3 in a 24 hour period, inclusive. |dw:1433136689393:dw|
anonymous
  • anonymous
and 2 high tides
anonymous
  • anonymous
and you can go off that same chart to get both? I'd think so since high and low are both on there
anonymous
  • anonymous
yes you can
anonymous
  • anonymous
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
anonymous
  • anonymous
No I think that's it :)

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