Question

Cos^2a=cos^2a-sin^2a for all values of a.

Answer 1

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Explanation:

just got it correct on apx

Answer 2

Explanation:

`cos2a=cos^2a-sin^2a`

Lets derive this equation,

we can write ,

`cos2a= cos(a+a)`

going by the identity,

`cos(a+b)= cosa cosb - sina sinb`

using the identity ,

`cos(a+a)= cosacosa-sinasina` .................(1)

After simplification of equation no.1 we get -

`cos(2a)=cos^2a-sin^2a` ............... (for any value of a)

Hence the equation is proved for every value of a.