Drawing method of angle bisector ruler: take point D as a circle with any radius, pass through two sides at two points, take these two points as the center of the circle respectively, take a distance greater than two points to make two circles and give them to another point D 1, and connect DD 1 as the bisector.

AD is high, so ∠ADC=90 degrees, DD 1 bisector, so one angle is 45 degrees, while the outer bisector angle DAM=90 degrees, and the triangle is a right isosceles triangle.