3sin²a+2sin²b=1
3sin^2a=1-2sin^2b=cos2b
所以
3sin2a-2*3sin^2a=0
3(2sinacosa-2sin^2a)=0
6sina(cosa-sina)=0
因为a是锐角,所以,sina>0,所以
cosa-sina=0
tana=1
a=π/4
sina=cosa=√2/2
2sin^2b=1-3sin^2a=1-3/2=1/2
-----------题目有问题