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September 3, 2015
Posted by **rick** on Tuesday, February 26, 2008 at 1:26pm.

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

- trig -
**drwls**, Tuesday, February 26, 2008 at 5:47pmUse 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