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Math Help - Right triangle in trig

  1. #1
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    Smile Right triangle in trig

    Hi, I am having trouble with this problem. My Geometry text book explains how to do this, but not very well, and I have come to a problem on a practice test that is nothing like what's in the book. I would really appriciate some help with this please!

    *Figure is a right triangle

    Question: Given the Figure below (right triangle), find ,
    a if sin B = 0.42, cos B = 0.91, tan B = 0.47 and c =60

    Thank you very very much!
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  2. #2
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    Quote Originally Posted by Polkadotprincess19 View Post
    Hi, I am having trouble with this problem. My Geometry text book explains how to do this, but not very well, and I have come to a problem on a practice test that is nothing like what's in the book. I would really appreciate some help with this please!

    *Figure is a right triangle

    Question: Given the Figure below (right triangle), find ,
    a if sin B = 0.42, cos B = 0.91, tan B = 0.47 and c =60

    Thank you very very much!
    Since you know the value of sin B and c, you could simply use the equation
    sin B=b/c
    to calculate b and then plug this into Pythagorean theorem
    a^2+b^2=c^2
    to get a.

    But even simpler: If you know that in right triangle sin A=cos B, then you have
    cos B=sin A=a/c
    from which you can easily get a.

    (I guess that A is the angle opposite to the side a and B is the angle opposite to the side b - this is probably shown in the figure you did not show us. Am I right?)
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  3. #3
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    Quote Originally Posted by Polkadotprincess19 View Post
    Hi, I am having trouble with this problem. My Geometry text book explains how to do this, but not very well, and I have come to a problem on a practice test that is nothing like what's in the book. I would really appriciate some help with this please!

    *Figure is a right triangle

    Question: Given the Figure below (right triangle), find ,
    a if sin B = 0.42, cos B = 0.91, tan B = 0.47 and c =60

    Thank you very very much!
    1. Use the definition of the trigonometric functions in a right triangle:

    \sin(B)=\frac bc

    \cos(B)=\frac ac

    \tan(B)=\frac ba

    2. Choose the appropriate equation to calculate a.
    Attached Thumbnails Attached Thumbnails Right triangle in trig-trigfkt_defin.png  
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  4. #4
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    Ok, I found a figure online similar to the figure I am trying to solve. It's the same thing it's just flipped the opposite way.

    So, would I be doing the same thing that you told me to do?

    *figure in my book is flipped so A is facing the right.



    Thank you!
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