sin^8x+cos^8x+5cos2x/4=0
(sin^4x+cos^4x)^2-2sin^4xcos^4x+5cos2x/4=0
(1-2sin^2xcos^2x)^2-2sin^4xcos^4x+5cos2x/4=0
1-4sin^2xcos^2x+4sin^4xcos^4x-2sin^4xcos^4x+5cos2x/4=0
8sin^4xcos^4x-16sin^2xcos^2x+5cos2x+4=0
sin^42x-8sin^22x+10cos2x+8=0
(1-cos^22x)^2-8(1-cos^22x)+10cos2x+8=0
1-2cos^22x+cos^42x-8+8cos^22x+10cos2x+8=0
cos^42x+6cos^22x+10cos2x+1=0
(sin^4x+cos^4x)^2-2sin^4xcos^4x+5cos2x/4=0
(1-2sin^2xcos^2x)^2-2sin^4xcos^4x+5cos2x/4=0
1-4sin^2xcos^2x+4sin^4xcos^4x-2sin^4xcos^4x+5cos2x/4=0
8sin^4xcos^4x-16sin^2xcos^2x+5cos2x+4=0
sin^42x-8sin^22x+10cos2x+8=0
(1-cos^22x)^2-8(1-cos^22x)+10cos2x+8=0
1-2cos^22x+cos^42x-8+8cos^22x+10cos2x+8=0
cos^42x+6cos^22x+10cos2x+1=0