If `[sintheta+costheta]/[sintheta-costheta]=3`,then find the value of `sin^4theta-cos^4theta`

Explanation

`sin^4theta - cos^4theta = (sin^2theta+cos^2theta)(sin^2theta+cos^2theta) = sin^2theta - cos^2theta`


Now, `(sintheta+cos theta)/(sin theta - cos theta) = 3`

`=>(sintheta+cos theta)/(sin theta - cos theta)**(sin theta + cos theta)/(sin theta + cos theta) =3`

`=>(sintheta+costheta)^2 = 3(sin^2theta - cos^2theta)`

`=>sin^2theta - cos^2theta = 1/3(sintheta+costheta)^2->(1)`


Also, `(sintheta+cos theta)/(sin theta - cos theta) = 3`

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