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Math Help - [SOLVED] Proving

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    [SOLVED] Proving

    Without using a calculator, prove that x = \frac{\pi}{10} satisfies the equation  \sin 3x = \cos 2x .
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    Quote Originally Posted by mark1950 View Post
    Without using a calculator, prove that x = \frac{\pi}{10} satisfies the equation  \sin 3x = \cos 2x .
    \cos(2x) = \sin\left(\frac{\pi}{2} - 2x\right)

    for x = \frac{\pi}{10} ...

    \sin\left(\frac{\pi}{2} - \frac{2\pi}{10}\right) = \sin\left(\frac{3\pi}{10}\right) = \sin(3x)
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