sin^4x+cos^4x-cos2x=0,5

(sin^2x+cos^2x) ^2-2sin^2xcos^2x-cos2x=1/21-sin^2 (2x) /2-cos2x=1/21-1/2 (1-cos^2 (2x) -cos2x=1/21/2cos^2 (2x) -cos2x=0cos2x (1/2cos2x-1)=0x=П/4+ Пk/21/2cos2x=1 нет решения |cosx| <= 1