angle bisectors on a grid

a ppt is here

this is part of a series of tasks involving a square dot grid and, in this case, expressing an angle as arc tan (fraction)
exploring when angle bisectors passing through integer (dot) grid points

these were used in several tasks, part of a session at Anne Watson and John Mason's house looking at the topic of 'angle'

you could use a few of the initial tasks to practice bisecting an angle with ruler, pencil and compasses

but the work continues, to see how pythagorean triples are involved and how to calculate the radius of the incircle for such triangles