已知3sinα=-cosα,计算

2个回答

由3sinα=-cosα知tanα=-1/3
〔2(sinα)^2+3(cosα)^2〕/〔(sinα)^2+sinαcosα〕
=〔2(tanα)^2+3〕/〔(tanα)^2+tanα〕
=（2（-1/3）^2+3）/(（-1/3）^2-1/3)
=(29/9)/(-2/9)=-29/2