Cos^2 theta - sin^2 theta + sin theta = 0
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Cos^2 theta - sin^2 theta + sin theta = 0

[From: ] [author: ] [Date: 11-11-03] [Hit: ]
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i know the answer is 11pi/6 & 7pi/6 & pi/2


i know sin^2 theta = (1 - cos^2 theta)

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Since you already have two terms with sin, rewrite cos^2 as 1-sin^2:

Cos^2(θ)-sin^2(θ)+sin(θ)=0

1-sin^2(θ)-sin^2(θ)+sin(θ)=0

0= 2sin^2(θ)-sin(θ)-1

0= (2sinθ+1)(sinθ-1)

Sinθ=-1/2 or 1

(7pi/6, 11pi/6) or (pi/2) for θ in [0,2pi)

Hoping this helps!
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keywords: Cos,sin,theta,Cos^2 theta - sin^2 theta + sin theta = 0
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