In the triangle ABC, ab = AC, point D is on AC. when the angle a is equal to what degree, the triangle abd and the triangle BCD are isosceles triangles There is no graph, just let you find the angle a how many degrees

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• 1. In △ ABC and △ ACD, ∠ ACB = ∠ ADC = 90 °, AC = 5, ad = 4. When BC is equal to what, △ ABC is similar to △ ADC? Explain your reason Picture: a right triangle on the left is placed upright, with vertex a, bottom left B, bottom right C, ∠ C as right angle, and a right triangle on the right is smaller than △ ABC, one side is collinear with AC, two outer sides are right angles with D, ∠ d. A is also the vertex of the right triangle, and C is another point except vertex and right angle Answer before April 10
• 2. As shown in the figure, it is known that ad is the middle line of △ ABC, ∠ ADC = 45 ° turn △ ADC over along the straight line ad, and point C falls at the position of point C ' As shown in the figure, it is known that ad is the middle line of △ ABC, ∠ ADC = 45 °, turn △ ADC over along the straight line ad, point C falls at the position of point C ', BC = 4, and find the square of the length of BC' I haven't thought about them for a long time
• 3. It is known that adae is the middle line and height of triangle ABC respectively. The perimeter of triangle ABC is 3 cm larger than that of triangle ACD, and ab = 3 cm Ask for the length of AC, Calculate the area relationship between △ abd and △ ACD
• 4. In s-abc, triangle △ ABC is an equilateral triangle with side length 4, plane sac ⊥ plane ABC, SA = SC = 2, M is the midpoint of ab (1) Find the size of dihedral angle s-cm-a; (2) find the distance from point B to surface SCM
• 5. How many points in the plane are equidistant from three points a B C that are not on the same line
• 6. ABC three points are in the same plane but not on the same straight line. You can draw three straight lines through these three points, right?
• 7. The distance from three points ABC not on the same straight line to plane a is equal, and a does not belong to a 1. At least one edge of triangle ABC is parallel to a 2. At most two sides of triangle ABC are parallel to a 3. Only one edge of triangle ABC intersects with a What are the correct ones?
• 8. It is known that △ ABC is not in plane α. If the distances from a, B and C to plane α are equal, then the positional relationship between plane ABC and plane α is______ ．
• 9. It is known that there are three points a and B. C on the sphere, which form an equilateral triangle with side length of 1. If the distance from the center of the sphere to the plane ABC is equal to 13 of the radius of the sphere, then the radius of the sphere is () A. 3B. 13C. 64D. 32
• 10. There are several planes which are 1cm away from the three vertices of △ ABC whose sides are 3cm As the title 2. How many out of plane lines are there in the 12 diagonals of the cuboid? 3. Let f (x) = 1 + X / 1-x, and let F 1 (x) = f (x), f K + 1 (x) = f (f K (x)), k = 1,2.. then f 2007 (x) =?
• 11. As shown in the figure, in △ ABC, ab = AC, ∠ a = 36 °, BD and CE are the bisectors of △ ABC and △ BCD, respectively, then the isosceles triangle in the figure has______ One
• 12. In the isosceles triangle ABC, AB equals AC equal to 13, BC equal to 10, D is the midpoint of AB, do de through D, perpendicular to AC and E, find de?
• 13. In the isosceles triangle ABC, the angle a is equal to 20 degrees, AB is equal to AC, D is on AC, and ad is equal to BC. Find the size of the angle abd
• 14. In non isosceles triangle ABC, D is the midpoint of BC and F is the midpoint of ab. the correct conclusion is that a AE: ad = 1:3, B △ abd is all equal to △ ADC, C △ abd is similar △ADC D △AEF=△CED
• 15. It is known that in △ ABC, be = CE, ∠ DBC = ∠ ACB = 120 °, BD = BC, CD intersection AB is at point e., and de = 3ce is proved
• 16. In △ ABC, ab = AC, ∠ a = 120 °, D is the midpoint of AB, crossing D as the vertical bisector of AB and crossing BC at e. the proof is EC = 2be
• 17. As shown in the figure, in the triangle ABC, ab = AC, the angle a = 120 ° de bisects AB and BC vertically in D, e
• 18. It is known that: as shown in the figure, in △ ABC, AC = BC, ∠ ACB = 120 °, CE is perpendicular to AB and D, and de = DC
• 19. In the triangle ABC, the angle ACB is 90 degrees, AC = BC, ad is the center line of DC side, CE is perpendicular to e, and the extension line of CE intersects AB at F Find the value of (1) AE ratio de and (2) Tan angle bad
• 20. As shown in the figure, in △ ABC, ad ⊥ BC, CE ⊥ AB, D and e respectively, ad and CE intersect at point h, please add an appropriate condition:______ So that △ AEH ≌ △ CEB