lim x-->0 (cos 3x-cos 5x)/x2
By using
cosC - cosD = -2 (sin(C+D)/2) (sin(C-D)/2 )
Lt x -->0 {-2 sin 4x -sin x} / x2
Lt x -->0 {2 sin 4x sin x) / v
Lt x -->0 { 2 (sin 4x )/4x (sin x)x } * 4x * x / x2
Ans = 8
lim x-->0 (cos 3x-cos 5x)/x2
By using
cosC - cosD = -2 (sin(C+D)/2) (sin(C-D)/2 )
Lt x -->0 {-2 sin 4x -sin x} / x2
Lt x -->0 {2 sin 4x sin x) / v
Lt x -->0 { 2 (sin 4x )/4x (sin x)x } * 4x * x / x2
Ans = 8