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i dont understand why there is -65(sinx)^4

Can anyone explain?

 May 25, 2017
 #1
avatar+9466 
+1

\(\dfrac{1}{2}\left(64(\cos^2\theta-\sin^2\theta)+\csc^2\theta\right)\\ =\dfrac{1}{2}\left(\dfrac{64\sin^2\theta\cos^2\theta-64\sin^4\theta+1}{\sin^2\theta}\right)\\ =\dfrac{1}{2}\left(\dfrac{64\sin^2\theta(1-\sin^2\theta)-64\sin^4\theta+1}{\sin^2\theta}\right)\\ =\dfrac{1}{2}\left(\dfrac{64\sin^2\theta-64\sin^4\theta-64\sin^4\theta+1}{\sin^2\theta}\right)\\ =\dfrac{1}{2}\left(\dfrac{-128\sin^4\theta+64\sin^2\theta+1}{\sin^2\theta}\right)\\\)

It's not correct, totally.

 May 25, 2017
 #2
avatar+118587 
0

I get the same as Max :)

 May 25, 2017

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