Question

已知cos(π/4 +x)=3/5，17π/12<x<7π/4，求(sin2x+2sin�0�5x)/1-tanx的值

Answer 1

您好：解答如下17π/12<x<7π/4，所以5π/3<π/4 +x<2π得到cos(π/4 +x)=3/5，sin(π/4 +x)=-4/5cosx=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/12<x<7π/4，所以sinx=-7√2/10，tanx=7sin2x=2sinxcosx=7/25(sin2x+2sin�0�5x)/1-tanx=（7/25+49/25）/（1-7）=-28/75谢谢采纳，有疑问欢迎您追问