Mathematics
GloriaHellwig946
2016-09-19 21:01:54
Find cos(20) if 0=pi/3
ANSWERS
Delora105
2016-09-19 21:38:21

[latex]f extit{Double Angle Identities} \ quad \ cos(2 heta)= egin{cases} cos^2( heta)-sin^2( heta)\ 1-2sin^2( heta)\ oxed{2cos^2( heta)-1} end{cases}\\ -------------------------------\\ cos(2 heta)implies 2cos^2( heta)-1qquad heta=frac{pi }{3}implies 2left[ cosleft( frac{pi }{3} ight) ight]^2-1 \\\ 2left[ cfrac{1}{2} ight]^2-1implies 2cdot cfrac{1}{4}-1implies cfrac{1}{2}-1implies -cfrac{1}{2}[/latex]

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