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 a real number is

The real value of theta for which the expression (1 + icos 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

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

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

The real vaule of theta for which the expression (1+icostheta)/(1-2icos theta) is a purely imaginary number is