Question

求sina^2cosa最小值

Answer 1

设 t=sina^2cosa

2t^2=(sina)^2*(sina)^2*2(cosa)^2

≤{[(sina)^2+(sina)^2+2(cosa)^2]/3}^3

=8/27

t^2 ≤4/27

-2√3/9≤t ≤2√3/9