Question

(1sin^2a+1cos^2a )*sin^22a

Answer 1

$=(dfrac{1}{sia^2a}+dfrac{1}{cos^2a})*(2sin a*cos a)^2=dfrac{cos^2a+sin^2a}{sin^2a*cos^2a}* \ \ *4sin^2a*cos^2a=dfrac{1}{sin^2a*cos^2a}*4sin^2a*cos^2a=1*4=4$