Question

What is exp(ja) equal to, where j is the square root of unity?

(a) cos ja + jsin a

(b) sin a + jcos a

(c) cos j + a sin j

(d) cos a + jsin a

The question was asked in an interview.

This interesting question is from The Complex Exponential topic in section Signals and Systems Basics of Signals and Systems

Answer 1

Correct option is (d) cos a + jsin a

For explanation: This is the corollary of DeMoivre/Euler’s Theorem.