Question

Lim x -> 0 (1-cos x)/ (cos 3x-cos x)

Answer 1

Ubah  bentuk 1 - cos x = 1 - (1 - 2 sin² 1/2 x) = 2 sin² 1/2 x
cos 3x - cos x  = 2 sin 2x . sin x

limit (x ->0)  [ 2 sin² 1/2 x ] / [ 2 sin 2x sin x ] 
= 2 (1/2)² / [ 2(2) ]
= (1/2) / (4) 
 = 1/8