3sin^2a+2cos^2b=2sina 则sin^2a+cos^b的取值范围是

问题描述:

3sin^2a+2cos^2b=2sina 则sin^2a+cos^b的取值范围是
我做了[0,1/2] 答案是[0,4/9]

因为sina有范围.由题设3sin^2a