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Math Help - Trigonometry Derivation Problem...please help :P

  1. #1
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    Trigonometry Derivation Problem...please help :P

    Hi, I need help trying figure out this problem: I'm trying to figure out the steps to get from one equation to another

    Starting Equation:
    Y = X (cos^2Ɵ) (cos^2(π/2 - Ɵ)

    **missing steps**

    Final Equation:
    Y = (X/4) sin^2(2Ɵ)


    If anyone can help I'd greatly appreciate it. Thanks!
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  2. #2
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    Re: Trigonometry Derivation Problem...please help :P

    You need to make use of the fact that \displaystyle \begin{align*} \cos{\left( \frac{\pi}{2} - \theta \right)} \equiv \sin{(\theta)} \end{align*} and \displaystyle \begin{align*} \sin{(2\theta)} \equiv 2\sin{(\theta)}\cos{(\theta)} \end{align*}.
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  3. #3
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    Re: Trigonometry Derivation Problem...please help :P

    Thanks, but what I really find what's throwing me off is the fact that both the cos are squared in the equation :S
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  4. #4
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    Re: Trigonometry Derivation Problem...please help :P

    It helps to remember that the product of squares is equal to the square of products...
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  5. #5
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    Re: Trigonometry Derivation Problem...please help :P

    I'm trying to use the "power reducing" trig identities on this website, but I'm still not getting it...this is driving me crazy
    Table of Trigonometric Identities
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  6. #6
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    Re: Trigonometry Derivation Problem...please help :P

    You are making life difficult on yourself. The only identities you need to use are the ones I gave you. The rest is algebra.
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    Re: Trigonometry Derivation Problem...please help :P

    Prove It has rightly guided you. However you may look at attached file for solutionTrigonometry Derivation Problem...please help :P-trig.png
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  8. #8
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    Re: Trigonometry Derivation Problem...please help :P

    Quote Originally Posted by ibdutt View Post
    Prove It has rightly guided you. However you may look at attached file for solutionClick image for larger version. 

Name:	Trig.png 
Views:	5 
Size:	5.6 KB 
ID:	27430
    You have a typo, the last line should be x/4, not x/2.
    Thanks from ibdutt
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