First, we can rewrite the numerator:
lim theta -> 0 (1 - cos theta)/theta = lim theta -> 0 2 sin(theta/2)^2/theta
We can then simplify and apply l'Hopital's Rule:
lim theta -> 0 2 sin(theta/2)^2/theta = lim theta ->0 4 sin (theta/2) cos(theta/2)/1 = 4.
Therefore, the limit is 4.