Question

sin^4theta+cos^4theta/1-2sin^2thetacos^2theta

Answer 1

In the numerator, use
${a}^{2} + {b}^{2} + 2ab = {(a + b)}^{2}$
then use
${( \sin( \alpha )) }^{2} + { (\cos( \alpha )) }^{2} = 1$