Cut a pizza into 3 equal pieces

How can you cut a pizza into 3 equal sized pieces with a single cut using a knife ?

Answer: 

Step 1 : make a cut from the perimeter straight to the centre . As shown from O to A.

Step 2 : fold the pizza across AB as shown. And make the cut OC at 120°

Step 3: open the pizza up to obtain three equal parts. Enjoy your perfect 1/3 slice