Evalue each of the following limits.

Ok I am having trouble with evaluating trig limits with the tan function. I was wondering if someone could show me step by step their answer for the following three questions:

a) lim (tanx)/(4x)

x-> 0

b) lim (x^3)/(tan^3(2x))

x->0

c) lim (2tanx)/(xsecx)

x->0

please explain it thoroughly as you can. Appreciate it very much. Thanks.