Homework Help: precalculus

Posted by ama on Friday, July 6, 2012 at 2:14am.

write each expression as the sine, cosine or tangent of a double angle. then find the exact value of the expression.

a. 2sin 22.5 cos 22.5

b. cos^2 105- sin^2 105

precalculus - Damon, Friday, July 6, 2012 at 4:27am
a, use
sin 45 = cos 45 = 1/sqrt 2

b, use
105 = (1/2) 210 which is 180 + 30
so use
sin 210 = -1/2
cos 210 = -sqrt 3/2

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