How Does Phase Difference Affect Amplitude in Transverse Wave Interference?

[Oijl]

Homework Statement

Having two identical waves, knowing how much they're out of phase with each other, how can I know the amplitude of the resulting wave (as a factor of the original amplitude)?

Homework Equations

The Attempt at a Solution

 

[rl.bhat]

Write down two wavw equations, say
A1 = Ao(sinwt + phy1) and A2 = Aosin(wt + phy2)
Add them to find the amplitude of the resultant wave.