sin^4+sin^2cos^2+cos^2a=

sin^4+sin^2cos^2+cos^2a=
sin^4+sin^2cos^2+cos^2a=

sin^4+sin^2cos^2+cos^2a=
原式 = sin²a(sin²a + cos²a) + cos²a
= sin²a · 1 + cos²a
=sin²a+cos²a
=1

sin^4a+sin^2acos^2a+cos^2a=sin^2a(sin^2a+cos^2a )+cos^2a=sin^2a+cos^2a=1

题目有点问题哦！