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The angle θ lies in Quadrant  II .

sinθ=34

What is cosθ ?

SamJones  Feb 21, 2018

Best Answer 

 #1
avatar+7056 
+2

sin2θ  +  cos2θ   =   1

 

(3/4)2  +  cos2θ   =   1

 

cos2θ   =   1 - (3/4)2

 

cos2θ   =   1 - 9/16

 

cos2θ   =   7/16

 

cos θ   =   ±√[ 7/16 ]

 

cos θ   =   ±√7 / 4

 

Since  θ  is in Quadrant II , cos θ is negative.

 

cos θ   =   - √7 / 4

hectictar  Feb 21, 2018
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1+0 Answers

 #1
avatar+7056 
+2
Best Answer

sin2θ  +  cos2θ   =   1

 

(3/4)2  +  cos2θ   =   1

 

cos2θ   =   1 - (3/4)2

 

cos2θ   =   1 - 9/16

 

cos2θ   =   7/16

 

cos θ   =   ±√[ 7/16 ]

 

cos θ   =   ±√7 / 4

 

Since  θ  is in Quadrant II , cos θ is negative.

 

cos θ   =   - √7 / 4

hectictar  Feb 21, 2018

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