f(0)=0
f(cos²α-4)>-f(4m-2mcosα)=f(-4m+2mcosα)
cos²α-4>-4m+2mcosα
cos²α-4+4m-2mcosα>0
m>(4-cos²α)/(4-2cosa)=(2+cosa)/2
cosa∈[0,1]
(2+cosa)/2∈[1,3/2]
所以m>3/2
f(0)=0
f(cos²α-4)>-f(4m-2mcosα)=f(-4m+2mcosα)
cos²α-4>-4m+2mcosα
cos²α-4+4m-2mcosα>0
m>(4-cos²α)/(4-2cosa)=(2+cosa)/2
cosa∈[0,1]
(2+cosa)/2∈[1,3/2]
所以m>3/2