Two parallel lines are cut by a transversal. One of the interior angles on the same side of the transversal is 124°. The bisectors of these two co-interior angles meet at P. What is the angle between the bisectors at P?

Explanation

1. 01

   The two co-interior angles are 124° and $180^\circ - 124^\circ = 56^\circ$.

2. 02

   Their halves are 62° and 28°.

3. 03

   These halves are two angles of the triangle formed at P, so the angle at $P = 180^\circ - 62^\circ - 28^\circ = 90^\circ$.