已知cos(π/4+x)=3/5,(1π)12

问题描述:

已知cos(π/4+x)=3/5,(1π)12求[sin2x+2sin^2(x)]/1-tanx的值

您好:
解答如下
17π/12得到cos(π/4 +x)=3/5,sin(π/4 +x)=-4/5
cosx=cos(π/4 +x-π/4 )
=cos(π/4 +x)cosπ/4+sin(π/4 +x)sinπ/4
=3/5×√2/2+(-4/5)×√2/2
=-√2/10
因为17π/12sin2x=2sinxcosx=7/25
(sin2x+2sin²x)/1-tanx=(7/25+49/25)/(1-7)=-28/75
谢谢采纳,有疑问欢迎您追问