若sin（x+3派）cos(x-派)=2a+1,求实数a的取值范围

若sin（x+3派）cos(x-派)=2a+1,求实数a的取值范围
若sin（x+3派）cos(x-派)=2a+1,求实数a的取值范围

若sin（x+3派）cos(x-派)=2a+1,求实数a的取值范围
sin（x+3派）cos(x-派)
=(-sinx)(-cosx)
=sinxcosx
=1/2*sin2x
则-1/2

sinB=AC/AB=1/5
AC=AB/5
由勾股定理
AB2=AC2+BC2
则AB2=AB2/25+4
AB2=4÷24/25=25/6
AB=5√6/61454141