Mathematical geometry problem -- in the isosceles triangle ABC, ab = AC, the perpendicular of edge AB intersects with the straight line where AC lies In the isosceles triangle ABC, ab = AC, the acute angle obtained by the intersection of the middle perpendicular of side AB and the line where AC is located is 40 degrees, then the degree of ∠ B is?

Mathematical geometry problem -- in the isosceles triangle ABC, ab = AC, the perpendicular of edge AB intersects with the straight line where AC lies In the isosceles triangle ABC, ab = AC, the acute angle obtained by the intersection of the middle perpendicular of side AB and the line where AC is located is 40 degrees, then the degree of ∠ B is?

In the isosceles triangle ABC, ab = AC (angle B = angle c), the perpendicular line of AB (perpendicular foot set as e) intersects the straight line of AC at point F, and the acute angle AFE is 40 degrees. Then a new right triangle AEF is formed. The middle angle AEF is 90 degrees, and the angle AFE is 40 degrees