As shown in the figure, in △ ABC, ab = AC, ∠ B = 30 °, the vertical bisector EF of AB intersects AB at point E, BC at point F, EF = 2, then the length of BC is______ ．

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• 1. In △ ABC, ab = AC, ∠ B = 30 °, the vertical bisector EF of AB intersects AB at point E and BC at point F. if CF = 6 cm, then BF =? Cm
• 2. As shown in the figure, AE bisects ∠ BAC, BD = DC, de ⊥ BC, EM ⊥ AB, en ⊥ AC
• 3. As shown in the figure, AE bisects ∠ BAC, BD = DC, de ⊥ BC, EM ⊥ AB, en ⊥ AC
• 4. As shown in the figure, AE bisects ∠ BAC, BD = DC, de ⊥ BC, EM ⊥ AB, en ⊥ AC
• 5. As shown in the figure, AE bisects ∠ BAC, BD = DC, de ⊥ BC, EM ⊥ AB, en ⊥ AC
• 6. In the RT triangle ABC, the angle B = 90 ° ED is the vertical bisector of AC, intersecting BC and AC at points E and D respectively, connecting AE, if the angle BAE: the angle BAC = 1:5
• 7. It is known that in △ ABC, D is the midpoint of AB, e is the point on AC, EF ‖ AB, DF ‖ be. (1) conjecture: the relationship between DF and AE is______ Try to explain the correctness of your conjecture
• 8. In the triangle ABC, point O is a moving point on the side of AC. when passing through point O, a straight line Mn is parallel to BC. Let the bisector of the intersection angle BCA of Mn be at e, and the bisector of the intersection angle BCA be at E Bisector at point F. (1) proof; EO = fo, (2) when point O moves to where, quadrilateral aecf is rectangular, prove your conclusion
• 9. As shown in the figure, in △ ABC & nbsp;, point O is a moving point on the edge of AC, and a straight line Mn ‖ BC is made through point O. suppose that the angular bisector of Mn intersecting ∠ BCA is at point E, and the outer angular bisector of intersecting ∠ BCA is at point F. (1) try to explain EO = fo; (2) when point O moves to where, is the quadrilateral aecf rectangular? (3) when the point O moves to where, and what condition does △ ABC satisfy, the quadrilateral aecf is a square? And explain the reason
• 10. As shown in the figure, in the triangle ABC, point O is a moving point on the side of AC. a straight line Mn is parallel to BC through point O, and the bisector of Mn ∠ BCA is set at point E, The bisector of the outer angle of intersection ∠ BCA is at point F (1) try to explain: EO = fo; (2) when point 0 moves to where, the quadrilateral aecf is a rectangle? And explain the reason
• 11. In the triangle ABC, the angle BAC = 135 degrees, Fe and GH are the vertical bisectors on both sides of AB and AC respectively, and intersect with BC at points E and G to find the degree of angle EAG
• 12. As shown in Figure 6, in △ ABC, the vertical bisector Mn of ∠ a = 105 ° AC intersects at point n, AC intersects at point m, and ab + BN = BC,
• 13. As shown in the figure, ABC = ADC = 90 °, M is the midpoint of AC, Mn ⊥ BD and N, and BN = nd is proved ditto
• 14. As shown in the figure, it is known that in △ ABC, the bisector of ∠ ABC intersects with the vertical bisector of AC side at point n, passing through point n makes nd ⊥ AB at D, NE ⊥ BC at e, and proves ad = C Verification: ad = CE
• 15. Known: as shown in the figure, BD is the angular bisector of △ ABC, EF is the vertical bisector of BD, and intersects AB at e and BC at point F
• 16. Known: as shown in the figure, BD is the angular bisector of △ ABC, EF is the vertical bisector of BD, and intersects AB at e and BC at point F
• 17. In the right triangle, ∠ ACB = 90 °, CD is high, e is the middle point of BC, the extended line of ED and the extended line of Ca intersect at point F, and AC: BC = DF: CF is calculated
• 18. In △ ABC, ACB is 90 ° and CD ⊥ AB is made at d through point C. e is the midpoint of BC. Connect ed and extend the extension line of intersection CA to F. verify: AC / DF = BC / CF In △ ABC, ∠ ACB = 90 °, make CD ⊥ AB at d through point C, e is the midpoint of BC, connect ed and extend the extension line of intersection Ca at F. verification: AC / DF = BC / CF
• 19. In the triangle ABC, the vertical bisectors of edges AB and AC intersect point P. it is proved that point P is on the vertical bisector of BC It's an equilateral triangle
• 20. It is known that the abscissa of point a (- 2,0), B (4,0) P on the image of function y = 1 / 2x + 2 is m. when the triangle PAB is a right triangle, the value of M is obtained When p is a right angle