In the triangular prism ABC = a1b1c1, ab = Aa1 and cab = 90 degrees 1) It is proved that CB1 is perpendicular to BA1 (2) Given AB = root 2, BC = heel 5, find the volume of the triangular pyramid c1-aba1

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• 1. In the right triangle ABC, the angle ACB is equal to 90 degrees, CD is perpendicular to AB, and the perpendicular foot is d. let BC be equal to a, AC be equal to B, AB be equal to C, CD be equal to H
• 2. On the mathematical problems of Liberal Arts in senior high school about the proof of plane geometry If a vertex B and C that circle △ ABC, and give AB and AC to point D and point e respectively, the problem of AD: AC = AE: AB is not given graphics... I'm liberal arts, so don't use science knowledge to solve it... Otherwise I can't understand it... Thank you!
• 3. Let P, a, B and C be the four points on the surface of ball o, PA, Pb and PC are perpendicular, and PA = Pb = PC = 1, then the surface area of ball o is______ ．
• 4. As shown in the figure, there are four points P, a, B and C on the sphere. If PA, Pb and PC are perpendicular to each other, and PA = Pb = PC = a, the surface area of the sphere is______ ．
• 5. As shown in the figure, there are four points P, a, B and C on the sphere. If PA, Pb and PC are perpendicular to each other, and PA = Pb = PC = a, the surface area of the sphere is______ ．
• 6. There are four points P, a, B, C on the sphere, PA, Pb, PC are perpendicular, PA = 3, Pb = 4, PC = 5, so how to calculate the sphere area?
• 7. In the parallelogram ABCD, we know AB = 10, root 3, B = 60 ° and AC = 30, then we can find the area of the parallelogram Speed, speed! Thank you! ~
• 8. If all the vertices of a cuboid are on the same sphere and the lengths of the three edges on one vertex are 1, 2 and 3 respectively, the surface area of the cuboid is 0______ ．
• 9. If x = 1 and 1 / 5 minus 9 / 20, y = 1 and 9 / 5 times 6 / 7, then are x and Y reciprocal
• 10. Number reasoning 8,11,4,5,21,20,11 () Civil servants, why
• 11. If the side of a regular triangular pyramid is a right triangle and the side length of its bottom is a, then the side area of the pyramid is. Please attach a picture
• 12. If the sides of a regular triangular pyramid are right triangles and the length of its bottom side is a, then its total area is?
• 13. If the side length of the bottom is a and the sides are right triangles, calculate the side area It's a regular pyramid
• 14. If the side length of the bottom is a, then the total area of the pyramid is a______ ．
• 15. It is known that the side edge length of p-abc is 10cm, and the side area is 144cm. The side length and height of p-abc are calculated
• 16. For the vertex of △ ABC, find (1) the coordinate of the center of gravity of △ ABC, (2) the linear equation of the area of △ ABC through point a
• 17. Let vertex a (1,1) B (5,3) C (4,5) be the vertex of △ ABC, find the coordinates of the center of gravity of △ ABC (1), the area of △ ABC passing through point a, etc (2) A linear equation that bisects the area of △ ABC through point a
• 18. If the four vertices of a regular triangular pyramid are on a sphere with radius 1, and the three vertices of the bottom surface are on a big circle of the sphere, then the volume of the regular triangular pyramid is___ ．
• 19. If the four vertices of a regular triangular pyramid are on a sphere with radius 1, and the three vertices of the bottom surface are on a big circle of the sphere, then the volume of the regular triangular pyramid is___ ．
• 20. If the four vertices of an equilateral pyramid are on a sphere of radius 1, and the three vertices of the bottom surface are on a big circle of the sphere, then the volume of the equilateral pyramid is The answer to this question is that the bottom is an equilateral triangle and the radius of the ball is 1 The side length of the bottom surface is √ 3, The bottom area is 3 √ 3 / 4, ∴V=1／3×3√3／4×1=√3／4． I want to know why the side length of the bottom is root three. Is there any formula