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anonymous
 5 years ago
use double angle formula to find the exact value of 2cos^2(3pie/8)1
anonymous
 5 years ago
use double angle formula to find the exact value of 2cos^2(3pie/8)1

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anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0Use the fact that\[\cos{2 \theta}=\cos^2 \theta \sin^2 \theta=2\cos^2 \theta 1\]

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0For\[\theta = \frac{3\pi}{8}\]\[\cos 2 \theta =\cos \frac{3 \pi}{4}=\cos^2 \frac{3 \pi}{8}1\]The righthand side is your expression. Now

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0\[\frac{3\pi}{4}\] lies in the second quadrant where cosine is negative. 3pi/4 is equivalent to 135 degrees. The cosine of 135 degrees is equal to the the negative cosine of 45 degrees, which has an exact value of \[\frac{1}{\sqrt{2}}\]

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0become a fan! would love the points

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0what is the exact value of 2sin 157.5 cos 157.5

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0This is an example of double angle for sine.\[\sin 2 \theta = 2 \sin \theta \cos \theta\]Here theta is 157.5, so 2 x theta = 315 degrees. 315 = 360  45 This lies in the fourth quadrant where sine is negative. You have sin(315)=sin(45)= 1/sqrt(2) again.

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0it says write the following expression as sin cos or tan of a double agent. then find the exact value
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