Prove each identity. 1.-> cos^2x-sin^2x=2cos^2x-1

identites include-

cscx=1/sinx , secx=1/cosx , cotx=1/tanx , tanx=sinx/cosx , cotx=cosx/sinx , sin^2x+cos^2x=1

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In order to prove this identity, you need to start with one side, and then using existing identities, end up at the other side of the identity.

`LS=cos^2x-sin^2x` use `sin^2x+cos^2x=1`

`=cos^2x-(1-cos^2x)` remove brackets

`=cos^2x-1+cos^2x` collect like terms

`=2cos^2x-1`

`=RS`

**The identity has been proven.**

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