SOLUTION: find the exact value using a double angle identity cos(450)

Question 767420: find the exact value using a double angle identity
cos(450)
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
find the exact value using a double angle identity
cos(450)
***
cos2x=cos^2x-sin^2x
cos(450)=cos(2*225)=cos^2(225�)-sin^2(225�)
cos(225�)=-√2/2�in Q3
cos^2(225�)=2/4=1/2
sin(225�)=-√2/2�in Q3
sin^2(225�)=2/4=1/2
cos(450)=cos(2*225)=cos^2(225�)-sin^2(225�)=1/2-12=0
calculator check:
cos 450�=0
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