К.
Катя ............
sin^4 x + cos^3 x = 1
(1-cos^2 x)^2 + cos^3 x = 1
1 - 2 cos^2 x + cos^4 x + cos^3 x = 1
cos^4 x + cos^3 x - 2 cos^2 x = 0
cos^2 x (cos^2 x + cos x - 2) = 0
cos^2 x = 0
или
cos^2 x + cos x - 2 = 0
cos x = 0
или
cos x = 1 или cos x = -2
cos x = 0
или
cos x = 1
x = п/2 + пk, где k = ...-1, 0, 1...
или
x = пk, где k = ...-1, 0, 1...