Hi!

I just started up some repetition but got stuck when I looked at my techers answers.

I have this equation: x´´ + (k/m)x = 0

Then I get from the auxilliary solution that: x = Acos(sqrt(k/m))

However my teacher has written: x = Acos(sqrt(k/m)+a)

So he has some phase-constant a, and here is my question.

I see that this isnt that strange but how did it enter? Can someone show it to mathematically? Logically I think it makes sence but I'd like to see how.

Thanks for answers.