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

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Question 767420: find the exact value using a double angle identity
cos(450)
Answer by lwsshak3(11628) About Me  (Show Source):
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find the exact value using a double angle identity
cos(450)
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cos2x=cos^2x-sin^2x
cos(450)=cos(2*225)=cos^2(225º)-sin^2(225º)
cos(225º)=-√2/2 in Q3
cos^2(225º)=2/4=1/2
sin(225º)=-√2/2 in Q3
sin^2(225º)=2/4=1/2
cos(450)=cos(2*225)=cos^2(225º)-sin^2(225º)=1/2-12=0
calculator check:
cos 450º=0