I've drawn two random, non-parallel, straight lines on a plane. They cross over, forming two angles, a and b, where (a + b + a + b) = 1 (or 360°) and a ≤ b. (Making a either the acute angle or a right angle.)
Using only a compass and stright edge, how would I find the value of a? It is acceptable to use an infinite number of steps.
(This is an abstract recreational puzzle rather than a practical question. If it were practical, I'd aquire a protractor.)