How do you solve Cos (2theta) = -sqrt3 / 2cos(2θ)=−√32?

1 Answer
Binayaka C.
Apr 25, 2016

theta = 75^0, 105^0 , 255^0,285^0θ=750,1050,2550,2850 where theta<360θ<360

Explanation:

we know cos(180-30)=-sqrt3/2 or cos150=-sqrt3/2 :. 2 theta=150 or theta=75^0 Also cos(180+30)=-sqrt3/2 or cos210=-sqrt3/2 :. 2 theta=105 or theta=105^0 Similarly cos(540-30)=-sqrt3/2 or cos510=-sqrt3/2 :. 2 theta=255 or theta=255^0 Also cos(540+30)=-sqrt3/2 or cos570=-sqrt3/2 :. 2 theta=570 or theta=285^0[Ans]

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