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Given sin x = 0.9, what is cos x ?

(As a decimal rounded to the nearest hundreth)

 Apr 24, 2018
 #1
avatar+101088 
+2

sin x  =  9/10  = y/r

 

So....cos x / r

 

To find x

 

  x  = ±√[r^2- y^2 ]  =  ±√[ 10^2  - 9^2]  =  ±√[100 - 81 ]  = ±√19

 

So....depending upon where x  lies

 

cos x  = √19 /100  ≈ .04    or    cos x  ≈  -.04  

 

 

cool cool cool

 Apr 24, 2018

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