trig

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Prove the identity
sin (3 pi/2 + x) + sin (3 pi/2 -x) = -2 cos x

  • trig -

    Use the identities
    sin (a + b) = sin a cos b + sin b cos a
    sin (a - b) = sin a cos b - sin b cos a
    and the facts that sin 3 pi/2 = -1 and cos 3 pi/2 = 0

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