Cutting particleboard shelf

[pete6032]

I will be putting up some shelving in my closet. Plan to buy some particleboard shelf from a big box store and run it along two sides of the closet. Where the sides meet I plan to do a 45 degree cut in each board. What is the best way to make this cut? One board will be 8 feet long. Should I use a table saw, jig saw, circular saw?

 

[Greenman]

Why miter the corner at all? It's particle board in a closet. Butt one piece into the other with a couple dowels or a piece of aluminum channel.
If your dead set on a miter, your best bet is a circular saw with a guide.

 

[herm0016]

butt joint. and circular saw with a high tooth count blade.