The standard equation of parabola with focus f (0, - 4) is?

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• 1. If we know that the focal coordinate of parabola is f (0, - 2), then its standard equation is?
• 2. It is known that the standard equation of parabola is a straight line x = - 2, and the focus is f (2,3). According to the definition of parabola, the equation of this parabola is obtained
• 3. Function of involute equation parameters of gears The two equations are as follows: Fang Chengyi angle=t*45 x=r*cos(angle)+pi*r*angle*sin(angle)/180 y=r*sin(angle)-pi*r*angle*cos(angle)/180 z=0 Fang Chenger afa=60*t x=r*cos(afa)+pi*r*afa/180 * sin(afa) y=r*sin(afa)-pi*r*afa/180 * cos(afa) z=0 In the two equations, angle = t * 45 and AFA = 60 * t are used to adjust the length of the involute, but the shape of the involute, that is, the shape of the gear, is unchanged, only the extension length of the involute is changed: if the value is set smaller, it may appear that the involute can not intersect the addendum circle, but the shape of the involute remains unchanged after changing the value?
• 4. In order to repair the damaged involute external gear, the diameter Da = 200.84mm, the gear z = 65, the full tooth height h = 6.60mm, the main parameters m, D, Da, DF and DB of the gear are determined
• 5. How to understand the gear involute equation of proe r = 36 theta = t * 45 x = R * cos (theta) + R * sin (theta) * theta * pi / 180 y = R * sin (th)
• 6. What is the modulus unit of involute gear and what is the standard pressure angle of involute cylindrical gear
• 7. (2010. Jingan District the first mock exam) the following curves can correctly indicate the rule of human digestive enzymes. A. I and III B. II and IV C. I and IV D. II and III
• 8. When the law of diminishing marginal returns takes effect, the total cost curve begins to change A. To decline at an increasing rate; B. to rise at an increasing rate; C. To decline at a decreasing rate; D. to rise at a decreasing rate Hello, I'd like to ask why we don't choose B. I think that when the law of diminishing marginal return comes into effect, that is, the law of increasing marginal cost comes into effect. At this time, the cost increases gradually, so the total cost rises at an increasing rate,
• 9. In the following curves, the law of human digestive enzyme action can be correctly expressed () A. I and III B. II and III C. I and IV D. II and IV
• 10. What are the nine conventional logging curves Petroleum Engineering, related. What are the nine conventional logging curves?
• 11. The distance from the focus to the collimator is 5, and the parabolic standard equation is solved RT.
• 12. The focal point F of the parabola is on the positive half axis a (M. - 3) of the x-axis, and the standard equation is solved on the parabola AF5
• 13. Let D: x ^ 2 + y ^ 2 + Z ^ 2 = a ^ 2, then what is the area of ∫ (x + y + Z) ^ 2ds curve divided into? (on D) The answer is 4 Π a ^ 4
• 14. Let ∑ be the cylinder x ^ 2 + y ^ 2 = a ^ 2 at 0
• 15. Let s be a sphere x ^ 2 + y ^ 2 + Z ^ 2 = 1, and find the value of surface integral ∫ (x + y + Z + 1) ds. The answer is 4 Π
• 16. What does DS represent in the surface integral of area in higher numbers
• 17. The projection of the intersection line of x ^ 2 + y ^ 2 under the equation z = x ^ 2 + y ^ 2 and z = 2-radical on xoy plane,
• 18. The equation for the projection of the sphere x ^ 2 + y ^ 2 + Z ^ 2 = 9 and the plane x + y = 1 on the xoy plane
• 19. ∫∫∑ 1 / √ (1 + 4x & # 178; + 4Y & # 178;) ds, ∑ surface z = x & # 178; + Y & # 178; (0 ≤ Z ≤ 1)
• 20. ∫ (X & ∫ 178; + Y & ∫ 178;) ds ∑: z = root X & ∫ + Y & ∫ 178; the part cut off by z = 2 ∫ ∫ is followed by ∑