Find the resulting amplitude `A'` and the phase of the vibrations `delta`
`S = Acos(omegat) + A/2 cos (omegat + pi/2) + A/2 cos (omega t + pi) + A/8 cos (omegat + (3pi)/(2)) = A' cos (omega t + delta)`

Answer

A, B, C

Explanation

`S = A cos omegat - A/2 sin omegat - A/2 cos omegat + A/8 sin omegat`
`= A/2 cos omegat - (3A)/(8) sin omegat`
`= (5A)/(8) (4/5 cos omegat - 3/5 sinomegat) = (5A)/(8) cos(omegat + 37^(@))`
`rArr A' = (5A)/(8) , delta = 37^(@)`