Euclid Book 1 - Proposition 29
Parallel lines makes angles equal

Index --- introduction --- definitions --- axioms and postulates --- propositions --- other

To be proved: A straight line falling on parallel straight lines makes the alternate angles equal to one another, the exterior angle equal to the interior and opposite angle, and the sum of the interior angles on the same side equal to two right angles.

Step through proof by clicking on Next line:

There is a line EF crossing parallel lines AB and CD

Previous proposition - Next proposition

© Jo Edkins 2010 - Return to Euclid index