User:Oxygendruggy

The left angle is an often forgotten part of mathematics. It is what is left over after a right angle. So a right angle is defined as a 90 degree angle. This means that a left angle is the remaining 270 degrees.

Calnan, J. Chawner, E. Hogan, H., Stillman, B., Walls, G. (1955) The forgotten theories of mathematics Oxford: J.P. Pitman Ltd