Question

Which of the following signals is monotonic?

(a) x(t) = t^3 – 2t

(b) x(t) = sin(t)

(c) x(t) = sin^22(t) + cos^22(t) – 2t

(d) x(t) = log(cos(t))

This question was addressed to me in an interview.

This question is from Signal Classification and Properties topic in division Signals and Systems Basics of Signals and Systems

Answer 1

Right answer is (c) x(t) = sin^22(t) + cos^22(t) – 2t

To explain I would say: c) reduces to 1 – 2t, which is a strictly decreasing function.