Posted by **Abbey** on Wednesday, March 17, 2010 at 12:18am.

2) Use the sum and difference identites

sin[x + pi/4] + sin[x-pi/4] = -1

sinx cospi/4 + cosxsin pi/4 + sinx cos pi/4 - cosx sin pi/4 = -1

2 sin x cos pi/4 =-1

cos pi/4 = sqr2/2

2sin^x(sqrt2/2) = -1

sin x = -sqrt2

x = 7pi/4 and 5pi/4

Am I correct?

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