In △ ABC, if Tana = 2, then Sina =, a, √ 5 / 5, B, 2 √ 5 / 5, C - √ 5 / 5, D-2 √ 5 / 5

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• 1. In RT △ ABC, ∠ C = 90 °, AC = 3, BC = 2, Tana = cotb=
• 2. This is a problem of mathematical geometry. How to find the degree of ∠ a in triangle △ ABC AB = AC BC = BD ad = de = EB?
• 3. Mathematical geometry problem -- in the isosceles triangle ABC, ab = AC, the perpendicular of edge AB intersects with the straight line where AC lies In the isosceles triangle ABC, ab = AC, the acute angle obtained by the intersection of the middle perpendicular of side AB and the line where AC is located is 40 degrees, then the degree of ∠ B is?
• 4. In the isosceles triangle ABC, ab = AC, ad is the middle line on the bottom edge
• 5. In the isosceles triangle ABC, ab = AC = 5, then the diameter of the circumcircle of the triangle ABC is________ . I think the problem is similar to the lack of conditions,
• 6. It is known that in △ ABC, ab = AC, ⊙ o with ab as diameter intersects BC at D and AC at e. it is proved that △ Dec is an isosceles triangle Such as the title
• 7. As shown in the figure, CD is the height of the bottom edge ab of the isosceles triangle ABC. De is parallel to BC and intersects AC at point E. judge whether △ Dec is an isosceles triangle and explain the reason
• 8. (1) As shown in Figure 1, isosceles △ ABC and isosceles △ Dec have a common point C, and ∠ BCA = ∠ ECD, connect be and ad, if BC = AC, EC = DC, prove: be = ad. (2) if △ Dec is rotated around point C to figure 2, figure 3 and figure 4, other conditions remain unchanged, are be and ad still equal? Why?
• 9. In △ ABC, ab = AC, D and E are the midpoint of BC and AC respectively, and △ Dec is an isosceles triangle? RT= =
• 10. In RT triangle ABC, ∠ C = 90 °, ab = 2, radical 2, BC = radical 6, solve this right triangle
• 11. In △ ABC, if B = 5, ∠ B = π 4, Tana = 2, then Sina = 1___ ；a= ___ ．
• 12. In △ ABC, if B = 5, angle B = 45 ° and Tana = 2, then Sina =?, a =?
• 13. As shown in the figure, AP is the height of △ ABC, point DG is on AB and AC respectively, point E F is on BC, quadrilateral defg is rectangular, AP = h, BC = a, let DG = x, the area of rectangular defg is y, try a, h, X to represent Y
• 14. As shown in the figure, CD is the height on the hypotenuse of RT △ ABC, e is the midpoint of AC, and the extended line of ED intersects CB at point F. prove BD * CF = CD * DF
• 15. In triangle ABC, AC = BC, angle c = 90 degrees, points D and E are on BC and ab respectively, triangle ACD is congruent triangle AED
• 16. As shown in the figure, we know that D and E are two points on the side of AB and AC in △ ABC, ab = AC, please add another condition______ To make △ Abe ≌ △ ACD (just write one)
• 17. It is known that in the triangle ABC, ad and be are the heights on the sides of BC and AC, respectively. A vertical line AB passing D intersects F, B is intersected g, and the extension line of AC intersects H
• 18. As shown in the figure, in positive △ ABC, points m and N are on AB and AC respectively, and an = BM, BN and cm intersect at point O. if s △ ABC = 7 and s △ OBC = 2, then bmba = 1___ ．
• 19. As shown in the figure, in △ ABC, am and cm are bisectors of angles respectively. Through M, make de ‖ AC. verify: AD + CE = De
• 20. As shown in the figure, in the RT triangle ABC, there are two moving points P and Q, which start from point C and move to a at 3cm / s along CB Ba and B at 4cm / s along CA ab. when one point reaches the end point, the two points stop moving at the same time If t exists, the area of triangle PCQ is half that of triangle ABC. If t does not exist, please explain why