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In Angle QRS, QR=31.9, RS=25.2, and QS=37.6. To the nearest tenth, what is the measure of angle R?

 Jan 27, 2021
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Using the Law of Cosines

 

QS^2   = QR^2  +  RS^2    -2  ( 31.9 * 25.2)  cos  ( QRS)

 

(37.6^2   - 31.9^2  - 25.2^2)   /   [ -2 ( 31.9 * 25.2) ]   =   cos (QRS)

 

Taking the  cosine inverse  to find angle QRS  we have

 

arccos [ (37.6^2   - 31.9^2  - 25.2^2)   /   [ -2 ( 31.9 * 25.2) ] ]  = QRS  =  81.46°   =  81.5°

 

 

cool cool cool

 Jan 27, 2021

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