已知tanx=3,计算(4sinx-2cosx)/(5cosx+3sinx)的值

问题描述:

已知tanx=3,计算(4sinx-2cosx)/(5cosx+3sinx)的值

七分之五

9。上下同时除以cosX

tanx=sinx/cosx=3则 cosx,sinx均不为零,
所以(4sinx-2cosx)/(5cosx+3sinx)
=(4sinx/cosx-2)/(5+3sinx/cosx)
=(4tanx-2)/(5+3tanx)
=(4*3-2)/(5+3*3)
=10/14
=5/7

上下除cosx,
(12-2)/(5+9)=5/7