thanks.

]]>So I thought: replace every cos^2 with 1 - sin^2 and simplify. (I've left out some simplification steps ... you'll have to put them in yourself.)

Now to use the given equation:

Use this to simplify E by removing the highest power:

Go back to the given equation and use it again to remove the 4th power term:

therefore

QED.

Bob

]]>then prove that

It seems easy but I don't know why am I not able to solve it.

Pls help.....

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