1. As shown in the figure, in a quadrilateral, ab ‖ CD, points E and F are on the sides AD and BC respectively, connecting AC and intersecting EF with G, angle 1 = angle BAC 【1】 Verification of EF ‖ CD 【2】 If ∠ CAF = 15 °, 2 = 45 ° and 3 = 20 °, calculate the degree of ∠ B and ACD 2. As shown in the figure, it is known that AD and AE are respectively the middle line and high line of △ ABC, and ab = 5cm, AC = 3cm. Find the perimeter difference between [1] △ abd and △ ACD 【2】 If BF is the bisector of △ abd, what is the area of s △ BFD? 3. As shown in the figure, it is known that in △ ABC, the bisector of ad bisection ∠ BAC intersects BC at D, ∠ ABC, the bisector of ∠ ACB intersects ad at O, and goes through o to make OE ⊥ BC at E. try to guess the relationship between ∠ BOD and ∠ EOC, and prove your conclusion worry

1. As shown in the figure, in a quadrilateral, ab ‖ CD, points E and F are on the sides AD and BC respectively, connecting AC and intersecting EF with G, angle 1 = angle BAC 【1】 Verification of EF ‖ CD 【2】 If ∠ CAF = 15 °, 2 = 45 ° and 3 = 20 °, calculate the degree of ∠ B and ACD 2. As shown in the figure, it is known that AD and AE are respectively the middle line and high line of △ ABC, and ab = 5cm, AC = 3cm. Find the perimeter difference between [1] △ abd and △ ACD 【2】 If BF is the bisector of △ abd, what is the area of s △ BFD? 3. As shown in the figure, it is known that in △ ABC, the bisector of ad bisection ∠ BAC intersects BC at D, ∠ ABC, the bisector of ∠ ACB intersects ad at O, and goes through o to make OE ⊥ BC at E. try to guess the relationship between ∠ BOD and ∠ EOC, and prove your conclusion worry

1. (1) prove: because angle 1 = angle BAC, so ab | EF and because ab | CD, so EF | CD (2) because ab | CD, so angle BAF = angle 3 = 20 degrees, so angle B = 180 degrees - angle BAF - angle 2 = 115 degrees, angle 1 = angle Caf + angle 3 = 35 degrees, and because EF | CD, so angle ACD = angle 1 = 35 degrees 2, (1) because AB is a triangle ABC