You can use the following Taylor series expansion for sin(3x):
sin 3x = 3x -(1/2)(3x)^2 + (1/3!)(3x)^3 -...
Divide that by x and you get a limit of 3.
You could also use L'Hopital's rule.
lim f(x) sin 3x / x
x�¨0
1 answer