SOLUTION: find the exact value using a double angle identity cos(3pi/2)

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Question 767421: find the exact value using a double angle identity
cos(3pi/2)
Answer by lwsshak3(11628) About Me  (Show Source):
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find the exact value using a double angle identity
cos(3pi/2)
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cos(3π/2)=cos(2*3π/4)
cos2x=cos^2x-sin^2x
cos(2*3π/4)=cos^2(3π/4)-sin^2(3π/4)=(-√2/2)^2-(√2/2)^2=1/2-1/2=0
calculator check:
cos(3π/2)=0