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Can anyone provide steps that show that

 

cos2x / (cosx - sinx) = cosx + sinx

 

?? Thanks!

 Sep 19, 2018
 #1
avatar+101761 
+1

cos2x / (cosx - sinx) = cosx + sinx 

 

Note that cos 2x  =  cos^2x  - sin^2 x....= (cos x - sin x) (cos x + sinx ).....so we have

 

(cos^2x - sin^2x )  / ( cosx - sin x)

 

(cosx + sin x) (cos x - sin x)  / (cos x - sin x )        divide out the  (cosx - sinx)

 

cos x + sin x  =    the right hand side

 

 

cool cool cool

 Sep 19, 2018
 #2
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+1

Thank you so much! Didnt think of the (a+b)*(a-b) rule!

 Sep 19, 2018

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