# How does one calculate Fourier transform of Feynman propagator?

I am struggling with calculating the following integral on Sredinicki:

How did he get the second line of (10.6)? That is, how did he calculate the Fourier transform of Feynman propagator?

• The Fourier transform of 1 is a $\delta$-function. – user178876 Feb 23 at 18:26