Use (2.20) to show that the sum1.7 cos(20πt + 70 π/180) + 1.9 cos (20πt + 200π/108) reduce...

Use (2.20) to show that the sum

1.7 cos(20πt + 70 π/180) + 1.9 cos (20πt + 200π/108) reduces to A cos(20πt + φ), where

A = {[1.7 cos(70 π/180) + 1.9 cos(200 π/108)]2 + [1.7 sin(70π/108) + 1.9 sin(200π/180)]2}1/2=1.532

And

The value of φ, given in radians, corresponds to 141. 79º