In the parallelogram ABCD, e and F are the points on the edge of AD and ab respectively, and be = DF, be and DF intersect at point G

In the parallelogram ABCD, e and F are the points on the edge of AD and ab respectively, and be = DF, be and DF intersect at point G

It is proved that CN ⊥ be, CH ⊥ DF are made by C respectively, connecting CE and CF, ∵ s △ BCE = 12s, parallelogram ABCD = s △ DFC, ∵ 12 · DF · ch = 12 · be · CN, ∵ be = DF, ∵ CN = ch, ∵ GC bisection ∠ bgd (the point with equal distance to both sides of the angle is on the bisection line of the angle)