Prove the identity
sin (3 pi/2 + x) + sin (3 pi/2 -x) = -2 cos x
trig - drwls, Tuesday, February 26, 2008 at 5:47pm
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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