The following problem was given as an example by the professor but I can't seem to come up with the same answer as he did.
The answer he got was C1 = -2 and C2 = 1/4
I keep getting C1 = - 1/4 and C2 = - 1/2
There are three possibilities 1) He's wrong 2) I'm wrong or 3) we are both wrong.
I need to know which it is.
Can you show me how you would solve the problem and give me the correct answer?

Problem:
X = C1 cos4t + C2 sin4t is a solution for the differential equation X" + 16X = 0

The initial conditions are: X(pi/2) = -2 and X'(pi/2) = 1

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