(1)m=0时,f(x)=(1+cotx)sin²x=1+sinx*cosx=0.5sin(2x)+1
在区间[ π/8 ,3π/4 ]上的取值范围为[0.5 ,1.5 ]
(2)当tanα=2时,cotα=1/2,sin²α=4/5
3/5=f(α)=(1+1/2)(4/5)+m(-1/2)(cos(α+π/4-α+π/4)-cos(α+π/4+α-π/4))
=6/5+ (-m/2)(1-cos2α)
=6/5+ (-m/2)(1-1+2sin²α)
=6/5+ (-m/2)(2*4/5)
m=3/4