Limits with trig

Question

Hi, I really need help with the following : 

 

a) limx--->0 (1-cos2x)/(x)

 

b) limx--> 0 (1-cos2t) /(sin^2(3t))

Answer 1

You'll notice if you evaluate either of these AT x=0 you get 0/0, so you're going to need l'Hopitals rule. Take the derivative of top and bottom then evaluate.

Answer 2

Apply L'Hospital Rule.  Then plug in x=0 for each question.