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Find all angles in [0°, 360°]
sin 2θ= cosθ





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 Apr 18, 2016

Best Answer 

 #1
avatar+561 
+15

\(sin2\theta=cos\theta \)

Apply the double angle identity to sin2θ.

\(2sin\theta cos\theta=cos\theta \)

\(2sin\theta cos\theta-cos\theta=0\)

\((cos\theta)(2sin\theta-1)=0\)

\(cos\theta=0\)

\(\theta=90°,270°\)

\(2sin\theta-1=0\)

\(\frac{1}{2}=sin\theta\)

\(\theta=30°,150°\)

Therefore, θ can be equal to 30°, 90°, 150°, 270°

 Apr 18, 2016
 #1
avatar+561 
+15
Best Answer

\(sin2\theta=cos\theta \)

Apply the double angle identity to sin2θ.

\(2sin\theta cos\theta=cos\theta \)

\(2sin\theta cos\theta-cos\theta=0\)

\((cos\theta)(2sin\theta-1)=0\)

\(cos\theta=0\)

\(\theta=90°,270°\)

\(2sin\theta-1=0\)

\(\frac{1}{2}=sin\theta\)

\(\theta=30°,150°\)

Therefore, θ can be equal to 30°, 90°, 150°, 270°

Will85237 Apr 18, 2016

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