As shown in the figure, BD is divided into two parts, be is divided into ABC 2:5, DBE = 21 ° and the degree of ABC is calculated

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• 1. As shown in the figure, BD bisects ∠ ABC, be bisects ∠ ABC into two parts of 2:5, ∠ DBE = 27 ° and calculates the degree of ∠ ABC
• 2. BD bisects the angle ABC, be divides the angle ABC into 3:5, two parts, the angle DBE is equal to 15 degrees, and finds the degree of the angle ABC
• 3. BD bisects ∠ ABC, be divides ∠ ABC into two parts of 3:4, ∠ DBE = 8 degrees, and calculates the degree of ∠ ABC
• 4. It is known that ad is the bisector of the outer angle EAC of △ ABC, and ad ‖ BC, then the edge of △ ABC must satisfy______ ．
• 5. As shown in the figure, △ ABC, ab = AC, ad ‖ BC, then ad bisects ∠ EAC, try to explain the reason
• 6. As shown in the figure, it is known that ∠ B = ∠ C. If ad ‖ BC, does ad divide ∠ EAC equally? Please give reasons
• 7. As shown in the figure, ad is the angular bisector of the outer angle of the triangle ABC. The intersection of AD and the circumscribed circle of the triangle ABC is at point D
• 8. (the third power of 4B / 7 - the square of 7ab + the square of 2B / 5) △ the square of 2B / 5
• 9. If the two vertex coordinates a (- 4,0), B (4,0) of △ ABC and the perimeter of △ ABC are 18, then the trajectory equation of vertex C is___ ．
• 10. Given the vertex a (1,4) of △ ABC, if point B is on the Y axis and point C is on the line y = x, then the minimum perimeter of △ ABC is______ ．
• 11. BD score ∠ ABC, be score ∠ ABC is 2:5, DBE = 21 degrees, calculate the degree of ∠ ABC
• 12. As shown in the figure, ad is the middle line of △ ABC, AE: AC = 1:3, ad intersects be at point F, then the ratio of the area of △ ABC to the area of △ ABF is one
• 13. As shown in the figure, the midlines AD and be of △ ABC intersect at point F. what is the quantitative relationship between △ ABF and the area of quadrilateral cefd? Why?
• 14. As shown in the figure, we know that be ⊥ ad, CF ⊥ ad, and be = cf. please judge whether AD is the middle line of △ ABC or the angular bisector? Please state the reason for your judgment
• 15. As shown in the figure, in △ ABC, ab = AC, ad ⊥ BC at point D, point E on AC, CE = 2ae, ad = 9, be = 10, ad and be intersect at point F, then the area of △ ABC is______ ．
• 16. Triangle ABC, ab = AC, ad vertical BC, CECF are the triangles with ACB = 48 degrees intersecting ad at e, F, connecting be intersecting AC at g, and calculate the degree of angle AGF
• 17. As shown in the figure, in △ ABC, EF is the median line of △ ABC, D is a point on the side of BC (not coincident with B and C), ad and EF intersect at point O to connect de and DF. To make quadrilateral AEDF a parallelogram, conditions need to be added______ (only add one condition, the answer is not unique)
• 18. In the triangle ABC, ab = AC, D is the midpoint of AB, de ⊥ AB intersects AC at point E, the circumference of the triangle BCE is known to be 10, and ac-bc = 2, so the circumference of the triangle EBC can be obtained
• 19. In the triangle ABC, ab = AC, D is the midpoint of AB, De is perpendicular to AB, AC intersects with E, the circumference of EBC is known to be 10, and ac-bc = 1 The circumference of ABC
• 20. As shown in the figure, in △ ABC, AE is the angular bisector, and ∠ B = 52 °, C = 78 ° to find the degree of ∠ AEB