Question

已知tanx+4cotx=4求(sinx^3-2cosx)/(sinx+2cosx)

Answer 1

tanx+4cotx=4

tanx+4/tanx=4

tanx^2-4tanx+4=0

tanx=2

sinx^2=4/5

原式

=（sinx^2*tanx-2)/(tanx+2)

=(4/5*2-2)/(2+2)

=-1/10