turunan fungsi y = 4 sin x adalah ...

dy/dx (4 sin x)
= 4 d/dx (sin x)
= 4 lim h→0 [sin (x + h) - sin x) / h]
= 4 lim h→0 (sin x cos h + cos x sin h - sin x) / h
= 4 lim h→0 [sin x (cos h - 1)] / h + lim h→0 (cos x sin x) / h
= 4 sin x lim h→0 (cos h - 1) / h + cos x lim h→0 sin h / h
= 4 sin x (0) + cos x (1)
= 4 cos x