Question

1-sin^4a-cos^4a/cos^4a

Answer 1

Решение смотри в приложении

Answer 2

1-sIn^4a-cos^4a=1-(1-cos2a)²/4-(1+cos2a)²/4=
=(4-1+2cos2a-cos²2a-1-2cos2a-cos²2a)/4=(2-2cos²2a)/4=
=2(1-cos²2a)/4=sin²2a/2=4sin²acos²a/2=2sin²acos²a

(1-sin^4a-cos^4a)/cos^4a=2sin²acos²a/cos^4a=2sin²a/cos²a=2tg²a