limx→−1cos2−cos2xx2−x=

limx→−1cos2−cos2xx2−x=limx→−12sin(1+x)sin(x−1)x2+x=2limx→−1sin(x+1)x+1×sin(x−1)x=2limx+1→0sinx+1x+1limx→−1sinx−1x=21sin−1−1−1=2sin2