sin4次方X+cos四次方X
=(sin^2x+cos^2x)^2-2sin^2x*cos^2x
=1-1/2*(sin2x)^2 COSX=4/5 sinx=±3/5 sin2x=±24/25
=1-1/2*24^2/25^2
=1-12*24/625
=337/625