Упростить: 1-2sin^2(a)+sin^4(a)/1-2cos^2(a)+cos^4(a)

Question

Упростить: 1-2sin^2(a)+sin^4(a)/1-2cos^2(a)+cos^4(a)

Answer 1

=(1-sin^2(a))^2/(1-cos^2(a))^2=cos^4(a)/sin^4(a)=ctg^4(a)