# DTFT of inverse of any function

In my book solution is given like this. But i am solving like this , am i doing wrong??

## 1 Answer

Yes, you're doing it wrong. :) Inverse systems in time domain satisfy

$$h[n] * h_i[n] = \delta[n]$$

where $$*$$ denotes convolution and $$h_i[n]$$ is the impulse response of the inverse system. If you DTFT this equation, you'll get a).