Question

Evaluate (exp(-at)u(t))*u(t), u(t) being the heaviside function.

(a) (1-exp(at)) u(t)/a

(b) (1-exp(at)) u(-t)/a

(c) (1-exp(-at)) u(t)/a

(d) (1+exp(-at)) u(t)/a

The question was asked in an interview for job.

This interesting question is from Continuous Time Convolution in section Time-Domain Analysis of CT Systems of Signals and Systems

Answer 1

Right choice is (c) (1-exp(-at)) u(t)/a

The best explanation: Use the convolution formula.