Harmonic motion, finding analytic expressions for constants

[Linus Pauling]

1. Find analytic expressions for the arbitrary constants A and phi in Equation 1 (found in Part A) in terms of the constants C and S in Equation 2 (found in Part B), which are now considered as given parameters.
Express the amplitude A and phase phi (separated by a comma) in terms of C and S.




2. x(t) = Acos(omega*t + phi_
x(t) = Ccos(omega*t) + Ssin(omega*t)




3. I have found the following:

C = Acos(phi)
S = -Asin(phi)
C^2 + S^2 = A^2

And I am lost at this point.

 

[Linus Pauling]

Nevermind, I figured it out.