#3 only. Please help me! Thanks very much

The text gives a recursive algorithm (Algorithm 2) for calculating a^n for real values of a and nonnegative values of n. This algorithm takes Theta(n) time. Devise a faster algorithm that calculates a^n/2 and then squares this value to get a^n. Note that you will need a to figure out how to deal with odd values of n. Give Theta-notation for the time for this new algorithm