Question

A cosine wave voltage signal has a 10V RMS value and 60Hz frequency. Also at time, t=0, the value of the voltage signal is equal to its RMS value. Which of the following is the correct mathematical representation of the voltage signal?

(a) 10 cos(60t)

(b) 10 cos (120πt)

(c) 14.14 cos(60t + π/4)

(d) 14.14 cos(120πt + π/4)

The question was asked in a job interview.

My doubt is from Signals in portion Signals and Amplifiers of Electronic Devices & Circuits

Answer 1

Right answer is (d) 14.14 cos(120πt + π/4)

For explanation I would say: Only equation 14.14 cos(120πt + π/4)  satisfies all the given parameters.