已知cos2A=根号2/3,则sin4次方A+cos4次方A的值为 A13/18 B11/18 C7/9 D-1

B
sin^4a+cos^4a=(sin^2a+cos^2a)^2-2(sina*cosa)^2
=1-1/2*sin^2 2a
而因为cos2a=根2/3
所以cos^2 2a=2/9
sin^2a=7/9
代入得11/18