Specify a Fourier transform $ X(w) $
- $ X(w)=2\pi \delta\left ( w- \frac{\pi}{4}\right )+2\pi \delta\left ( w+ \frac{\pi}{4}\right ) $
Inverse Fourier transform of $ X(w) $
- $ \begin{align} x(t)&=\frac{1}{2\pi}\int_{-\infty}^{\infty}X( \omega)e^{j\omega t}d\omega \\& =\frac{1}{2\pi}\int_{-\infty}^{\infty}2\pi \delta\left ( w- \frac{\pi}{4}\right )e^{j\omega t}d\omega+ \frac{1}{2\pi}\int_{-\infty}^{\infty}2\pi \delta\left ( w+ \frac{\pi}{4}\right )e^{j\omega t}d\omega \\& =\int_{-\infty}^{\infty}\delta\left ( w- \frac{\pi}{4}\right )e^{j\omega t}d\omega+ \int_{-\infty}^{\infty}\delta\left ( w+ \frac{\pi}{4}\right )e^{j\omega t}d\omega \end{align} $
