已知函数Y=2sin^X+2sinXcosX-5cos^X 已知函数Y=2sin^X+2sinXcosX-5cos^X,

我想你的题目是：Y=2sin^2X+2sinXcosX-5cos^2X
Y=sin^2X+2sinXcosX+cos^2X+sin^2X-6cos^2X
=(sinX+cosX)^2+1-7cos^2X
=1+(sinX+cosX+√7cosX)(sinX+cosX-√7cosX)
接下来就很罗嗦了,asinX+bsinX=...要用到反三角函数.或者
=sin2X+2-7cos^2X
=sin2X+2-7(1-cos2X)/2
=-3/2+sin2X-(7/2)cos2X
.这题出的