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anonymous

  • one year ago

I need help on this, please? The vertices of a triangle are A(7, 5), B(4, 2), and C(9, 2). What is m? A. 30° B. 45° C. 56.31° D. 78.69°

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  1. misty1212
    • one year ago
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    HI!!

  2. anonymous
    • one year ago
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    hey

  3. misty1212
    • one year ago
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    that is a good question, what is \(m\)? not clear at all since none of the vertices are labelled "m"

  4. anonymous
    • one year ago
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    <ABC?* this was missing in the whole question, sorry

  5. misty1212
    • one year ago
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    here is a nice picture of your triangle i don't see any m in it though http://www.wolframalpha.com/input/?i=triangle+%287%2C+5%29%2C+%284%2C+2%29%2C+%289%2C+2%29

  6. anonymous
    • one year ago
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    yeah, that doesn't help me.. I don't even understand what the question is tell me nor Geometry it self?

  7. misty1212
    • one year ago
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    look carefully at your question you are given the vertices of a triangle, with points labelled A, B, C but then you ask for an angle m there is no m in sight, only A, B, C

  8. anonymous
    • one year ago
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    but thats all it gives me?? hmm?

  9. misty1212
    • one year ago
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    m usually stands for the measure of some angle but that would be "find m<A:for example

  10. jim_thompson5910
    • one year ago
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    \[\Large m\angle ABC\] means "angle ABC" where B is the vertex of the angle something like this |dw:1436923873975:dw|

  11. anonymous
    • one year ago
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    Here's the question, maybe this is better?

  12. jim_thompson5910
    • one year ago
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    First you use the distance formula to find the distance from A to B. That will give you the length of AB. Do the same for BC and AC

  13. jim_thompson5910
    • one year ago
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    tell me what distances you get

  14. anonymous
    • one year ago
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    Alrighty ^-^

  15. anonymous
    • one year ago
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    My work ^-^

  16. jim_thompson5910
    • one year ago
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    I don't agree with your last distance of 13

  17. jim_thompson5910
    • one year ago
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    you forgot to take the square root of 13

  18. anonymous
    • one year ago
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    oh

  19. anonymous
    • one year ago
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    Square root of 13 is 3.60

  20. jim_thompson5910
    • one year ago
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    |dw:1436929152566:dw|

  21. jim_thompson5910
    • one year ago
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    |dw:1436929181793:dw|

  22. jim_thompson5910
    • one year ago
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    a = 5 b = 3.60555 c = 4.24264 use these three values in the law of cosines formula b^2 = a^2 + c^2 - 2*a*c*cos(B) to solve for the value of B

  23. anonymous
    • one year ago
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    -173.8115277? Thats what I got?

  24. jim_thompson5910
    • one year ago
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    b^2 = a^2 + c^2 - 2*a*c*cos(B) 3.60555^2 = 5^2 + 4.24264^2 - 2*5*4.24264*cos(B) are you able to isolate cos(B) ? If not, try replacing "cos(B)" with "x" ie, solve for x in 3.60555^2 = 5^2 + 4.24264^2 - 2*5*4.24264*x

  25. anonymous
    • one year ago
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    For 5^2+4.24264^2-2*5*4.24264*x=42.99999417 then 3.60555^2 =12.9999908 and then I'm stuck, If I'm getting any of this right??

  26. jim_thompson5910
    • one year ago
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    `5^2+4.24264^2-2*5*4.24264*x` will turn into `42.9999941696 - 42.4264*x`

  27. jim_thompson5910
    • one year ago
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    42.9999941696 - 42.4264*x = 12.9999908025 -42.4264*x = 12.9999908025 - 42.9999941696 -42.4264*x = -30.0000033671 x = -30.0000033671/(-42.4264) x = ???

  28. anonymous
    • one year ago
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    Dont understand

  29. jim_thompson5910
    • one year ago
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    where are you stuck at?

  30. anonymous
    • one year ago
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    all of this.. I get .7071069751?

  31. jim_thompson5910
    • one year ago
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    yes x = 0.7071069751

  32. anonymous
    • one year ago
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    oh so I was doing all that right?

  33. jim_thompson5910
    • one year ago
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    you agree that 5^2 = 25 3.60555^2 = 12.9999908025 4.24264^2 = 17.9999941696 2*5*4.24264 = 42.4264 right?

  34. jim_thompson5910
    • one year ago
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    yeah if you got to x = 0.7071069751, then you are doing it right

  35. anonymous
    • one year ago
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    yeah and awesome

  36. jim_thompson5910
    • one year ago
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    recall that I replaced "cos(B)" with "x" to make things simpler

  37. jim_thompson5910
    • one year ago
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    if x = 0.7071069751 then cos(B) = 0.7071069751

  38. anonymous
    • one year ago
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    oooh theres more work???

  39. jim_thompson5910
    • one year ago
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    to find B itself, we apply the arccosine function to both sides cos(B) = 0.7071069751 arccos(cos(B)) = arccos(0.7071069751) B = ???

  40. jim_thompson5910
    • one year ago
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    just these last steps and you're done

  41. anonymous
    • one year ago
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    your killing me man, your killing me haha

  42. jim_thompson5910
    • one year ago
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    lol what is `arccos(0.7071069751)` equal to ?

  43. jim_thompson5910
    • one year ago
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    use a calculator like this one if you don't have a calculator with arccos http://web2.0calc.com/

  44. anonymous
    • one year ago
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    I got .7602444711?

  45. jim_thompson5910
    • one year ago
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    http://web2.0calc.com/#arccos(0.7071069751)

  46. jim_thompson5910
    • one year ago
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    once you click the link, hit enter to have it evaluate

  47. anonymous
    • one year ago
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    round it up its 45. Cool

  48. jim_thompson5910
    • one year ago
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    yeah 44.999984287488 ---> 45

  49. anonymous
    • one year ago
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    awesome, Its correct. Thank you, alot

  50. jim_thompson5910
    • one year ago
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    you're welcome

  51. anonymous
    • one year ago
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    Means a lot ^-^

  52. jim_thompson5910
    • one year ago
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    I'm glad to be of help

  53. anonymous
    • one year ago
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    Yay! lol

  54. ali2x2
    • one year ago
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    Close the question, But not before you give me a medal :3

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