The real value of `theta ` for which the expression `(1+icostheta)/(1-2icostheta)` is real number is

The real value of theta for which the expression (1+i cos theta)/(1-2i cos theta) is real number is

The real value of theta for which the expression (1 + icos theta)/(1 - 2i cos theta) is real number is

Find the real values of theta for which the complex number (1+i cos theta)/(1-2i cos theta) is purely real.

The real value of alpha for which the expression (1-i sin alpha)/(1+2i sin alpha) is purely real is

Find all values of theta for which (1-isintheta)/(1+icostheta) is purely real.