Докажите тождества 1/cos4x -1/ cos2x=sin2x/cos2x+sin4x/cos4x…

1) sin^2x+sin^2xcos^2x+cos^4x=1sin^2x (1+cos^2x)+cos^4x=1 (1=sin^2x+cos^2x) => sin^2x (sin^2x+cos^2x+cos^2x)+cos^4x=1sin^4x+2sin^2xcos^2x+cos^4x=1 (a^2+2ab+b^2)=(a+b) ^2 => (sin^2x+cos^2x) ^2=11^2=1