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Math Help - trig.

  1. #1
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    trig.

    Prove that the equation is an identity

    cosθ(secθ-cosθ)=sin^2 θ
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  2. #2
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    Hello blame_canada100
    Quote Originally Posted by blame_canada100 View Post
    Prove that the equation is an identity

    cosθ(secθ-cosθ)=sin^2 θ
    Two things you need to know here:

    • \sec\theta = \frac{1}{\cos\theta}


    • \sin^2\theta = 1-\cos^2\theta


    Grandad
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  3. #3
    Senior Member pacman's Avatar
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    cosθ(secθ-cosθ)=sin^2 θ, the left hand side of the equation seems tempting,

    cos θ (1/cos θ - cos θ) =

    cos θ (1/cos θ) - cos θ cos θ =

    1 - cos^2 θ = ?
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