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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,062

If

,then prove that

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

Pls help.....

friendship is tan 90°.

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,525

hi Niharika,

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

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,062

wow

thanks.

friendship is tan 90°.

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