In the triangle ABC, the bisector of angle ACB intersects AB at e, EF parallels BC, intersects AC at F, and the bisector of the outer angle of angle ACB intersects G Try to judge the shape of the triangle EFC and explain your reason

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• 1. The area of △ AEF is equal to the area of trapezoidal EFBC
• 2. As shown in the figure, D is the midpoint of BC, the length of ad is three times that of AE, the length of EF is three times that of BF, the area of triangle AEF is 18 square centimeters, and the area of triangle ABC is 18 square centimeters What's the square centimeter?
• 3. The triangle ABC, CE is perpendicular to AB, e, BF is perpendicular to AC, F, M is the midpoint of BC, EF is 5cm long, BC is 8cm long, find the perimeter of triangle EFM
• 4. As shown in the figure, △ ABC is an equilateral triangle, D is the midpoint of AB, de ⊥ AC is at e, EF ∥ AB intersects BC at F, CE = 3cm Find the circumference of (1) △ ABC; (2) Area of trapezoidal bdef
• 5. In △ ABC, DB and DC divide ∠ ABC and ∠ ACB equally, and intersect at point D, BG and CG divide ∠ CBE and ∠ BCF equally, and intersect at point G Verification: ∠ DBG = 90 degrees
• 6. If the triangle ABC is equal to the triangle def, the circumference of the triangle ABC is 70cm, De is 30cm, DF is 25cm, and the angle B is 25cm
• 7. It is known that △ ABC is all equal to △ def, the perimeter of △ ABC is 32, ab = 8, BC = 12, then CA =?, de =? EF =?
• 8. As shown in the figure, △ ABC rotates counterclockwise to the position of △ ab ′ C ′ so that AC bisects BB ′
• 9. Ask math question AA + BB + CC = ABC What are the ABC numbers?
• 10. Given a + B + C = 0, ABC = - 15, find AA (B + C) + BB (a + C) + CC (a + b)
• 11. As shown in the figure, in the triangle ABC, the bisector of angle ABC and angle ACB intersects at point O, passes through the point and makes EF parallel BC, intersects AB at e, intersects AC at F, and △ AB As shown in the figure, in the triangle ABC, the bisector of the angle ABC and the angle ACB intersects at the point O, passes through the point for EF parallel BC, intersects AB at e, intersects AC at F, and △ ab.% d% a as shown in the figure, in the triangle ABC, the bisector of the angle ABC and the angle ACB intersects at the point O, passes through the point for EF parallel BC, intersects AB at e, intersects AC at F, and the perimeter of △ ABC is 24cm, BC = 10cm, calculate the perimeter of the triangle AEF
• 12. In triangle ABC, the bisector of angle ABC and angle ACB intersects at point O, passes through point O for EF, is parallel to BC, intersects AB at point E, intersects AC at point F
• 13. As shown in the figure, it is known that in △ ABC, ∠ ACB = 90 °, D is a point on the extension line of BC, e is a point on AB, and it is on the vertical bisector eg of BD, When De is intersected with AC in F, AE = EF
• 14. As shown in the figure, in the triangle ABC, the angle ACB = 90 degrees, D is a point on the BC extension line, e is the intersection of BD vertical bisector and AB, and de intersects AC at point F Verification: point E is also on the vertical bisector of AF
• 15. As shown in the figure, in the triangle ABC, the angle ACB is equal to 90 degrees. D is a point on the extension of BC. E is the intersection of the vertical bisector of BD with ab. de intersects AC with F Prove that e bisects AF vertically
• 16. It is known that in △ ABC, ∠ ACB = 90 °, D is a point on the extension line of BC, e is a point on AB, and on the vertical bisector eg of BD, de intersects AC with F Verification: point E is on the vertical bisector of AF
• 17. The middle angle of the triangle ABC is ACB = 90 ° and D is on the extension line of BC. Eg bisects vertically, BD intersects AB on e, BD intersects g, de intersects AC on F. find: e is on the vertical bisector of AF
• 18. As shown in the figure, ∠ BAC = 106 ° in △ ABC, de and FG are the vertical bisectors of AB and AC respectively, then ∠ EAG=______ ．
• 19. In △ ABC and △ def, if ∠ a = D, ∠ B = e, ab = DF = 1, BC ratio EF = 3 to 2, then de = AC=
• 20. It is known that the three sides of △ ABC and △ def satisfy AB ／ de = AC ／ DF = BC ／ EF, and ∠ a = 56 °, B = 84 °, then ∠ d =, ∠ f =