As shown in the figure, in △ ABC, BD bisects ∠ ABC, de ‖ BC intersects AB at point E, EF ‖ AC intersects BC at point F. try to guess the size relationship between be and CF, and explain the reasons, as shown in figure.doc

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• 1. In △ ABC, ab = AC, D is a point on BC, de ⊥ AB and E, DF ⊥ BC, intersection AC and F, ∠ AFD = 160 °, find the degree of ∠ A and ∠ EDF RT
• 2. It is known that in the triangle ABC, the angle a is equal to 50 ° and DEF is the point on BC AB AC, DB= de.dc=df , find the angle EDF
• 3. In the triangle ABC, ab = AC, point D is on AC, and BD = BC = ad, De is the middle line of the triangle abd, and DF = BF, find the degree of ∠ EDF
• 4. As shown in the figure, in △ ABC, ab = AC, EB = BD = DC = CF, ∠ a = 40 °, then the degree of ∠ EDF is______ Degree
• 5. As shown in the figure: in △ ABC, D is the point on BC, de ⊥ Ba is in E, DF ⊥ AC is in F, and de = DF? And explain the reason
• 6. As shown in the figure: in △ ABC, D is the point on BC, de ⊥ Ba is in E, DF ⊥ AC is in F, and de = DF? And explain the reason
• 7. It is known that in the triangle ABC, D is a point of BC, De is perpendicular to AB and DF is perpendicular to AC and F, and De is equal to DF. What is the relationship between AD and ef D is a point on BC. I have the wrong number
• 8. As shown in the figure, circle O is the circumscribed circle of triangle ABC  
• 9. The three sides of a right triangle are 6 cm, 8 cm and 10 cm long respectively. What shape can be obtained by rotating the two right sides for one circle? What's the maximum volume of it?
• 10. The two right sides of a right triangle are 6cm and 10cm long respectively. What shape and volume can be obtained by rotating the right side of 10cm as an axis for one circle What's the volume, the formula
• 11. As shown in the figure, △ ABC, D is the midpoint of BC, e and F are two points on the edge of AB and AC respectively, ed ⊥ FD, which proves that be + CF > EF
• 12. It is known that: as shown in the figure, in △ ABC, ∠ B = ∠ C, points D, e and F are points on edges BC, AB and AC respectively, be = CD, connecting de and DF, with ∠ EDF = ∠ C, then are de and DF equal? Try to explain the reason
• 13. It is known that: as shown in the figure, in △ ABC, ∠ B = ∠ C, points D, e and F are points on edges BC, AB and AC respectively, be = CD, connecting de and DF, with ∠ EDF = ∠ C, then are de and DF equal? Try to explain the reason
• 14. In the triangle ABC, ab = AC, points D, e and F are on the sides of AB, BC and AC respectively. De = DF and EDF = angle a are known. Find out the similar triangles in the graph and prove them
• 15. In △ ABC, ab = AC, points D, e and F are on the sides of AB, BC and AC respectively, de = DF,
• 16. As shown in the figure, ab = De, AC ∥ DF, BC ∥ EF
• 17. In RT △ ABC, ∠ C = 90 °, a right triangle is solved by the following conditions (1) If we know that a = 4 times radical 3, B = 2 times radical 3, then C =? (2) If a = 10, C = 10 times the root 2, then ∠ B =? (3) If C = 20 and a = 60 ° are known, then a =? (4) If B = 35 and a = 45 ° are known, then a =?
• 18. In RT △ ABC, a = 30.01, ∠ B = 80 ° 24 'and ∠ C = 90 °, right triangle can be solved according to the following conditions
• 19. The side length of equilateral △ ABC is a, and the area of inscribed square defg of its inscribed circle is obtained
• 20. The square defg is the inscribed square of △ ABC, D is on ab. G is on AC, e and F are on BC, am ⊥ BC is on M, intersecting DG is on H. if ah is 4 and the side length of the square is 6, the length of BC is calculated