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Thread: Trig Identity problem

  1. #1
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    Trig Identity problem

    Hi guys,
    I am having trouble with my trig identities I think. I used the cofunction identity to solve what is below.

    If sin(48˚) is approximately .74. Use this estimate and the trig identities to find the following:

    cos(48˚)

    I've attached my work. However this is not the correct answer.

    Thank you for any advice.
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  2. #2
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    Re: Trig Identity problem

    the co-function identity would make finding $\cos(42^\circ)$ simple, however it's little help in finding $\cos(48^\circ)$ ...

    try a variation of the Pythagorean identity, $\cos^2{x}+\sin^2{x} = 1$ ...

    $\cos{x} = \sqrt{1-\sin^2{x}}$ for $0 \le x \le 90^\circ$
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  3. #3
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    Re: Trig Identity problem

    Quote Originally Posted by samcolette View Post
    Hi guys,
    I am having trouble with my trig identities I think. I used the cofunction identity to solve what is below.
    If sin(48˚) is approximately .74. Use this estimate and the trig identities to find the following:
    cos(48˚)
    $\cos(48^o)=\sqrt{1-\sin^2(48^o)}$
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