Math Problem Statement

The the points on the curve x2=8y nearest to the origin is

Solution

To find the point on the curve x2=8yx^2 = 8y that is nearest to the origin (0,0)(0,0), we need to minimize the distance between a point (x,y)(x, y) on the curve and the origin.

The distance DD from a point (x,y)(x, y) to the origin is given by:

D=x2+y2D = \sqrt{x^2 + y^2}

Since yy is a function of xx (from the curve equation), we can express DD in terms of xx only:

  1. The curve is given as x2=8yx^2 = 8y, so y=x28y = \frac{x^2}{8}.
  2. Substitute y=x28y = \frac{x^2}{8} into the distance formula:

D=x2+(x28)2D = \sqrt{x^2 + \left(\frac{x^2}{8}\right)^2}

To minimize DD, we can minimize D2D^2 instead, to avoid dealing with the square root:

D2=x2+x464D^2 = x^2 + \frac{x^4}{64}

Next, differentiate D2D^2 with respect to xx and set the derivative equal to zero to find the critical points:

d(D2)dx=2x+4x364=2x+x316\frac{d(D^2)}{dx} = 2x + \frac{4x^3}{64} = 2x + \frac{x^3}{16}

Set the derivative equal to zero:

2x+x316=02x + \frac{x^3}{16} = 0

Factor the equation:

x(2+x216)=0x\left(2 + \frac{x^2}{16}\right) = 0

This gives two cases:

  1. x=0x = 0
  2. 2+x216=02 + \frac{x^2}{16} = 0 which simplifies to x2=32x^2 = -32 (not possible since x2x^2 cannot be negative).

So, x=0x = 0 is the only solution.

Substitute x=0x = 0 into the curve equation x2=8yx^2 = 8y to find yy:

02=8y    y=00^2 = 8y \implies y = 0

Thus, the point on the curve nearest to the origin is (0,0)(0, 0).

Would you like more details or have any questions about this solution? Here are some related questions you might find interesting:

  1. How do you find the distance from a point to a curve in general?
  2. What is the method of Lagrange multipliers, and how is it used to solve constrained optimization problems?
  3. Can the distance formula be generalized to higher dimensions?
  4. What are the properties of the parabola x2=8yx^2 = 8y?
  5. How does the concept of minimizing distance relate to gradient descent methods?

Tip: In optimization problems, minimizing or maximizing a function often involves finding the derivative and solving for critical points where the derivative is zero.

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Math Problem Analysis

Mathematical Concepts

Geometry
Distance Formula
Optimization

Formulas

Distance formula
Optimization derivative

Theorems

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Suitable Grade Level

Grades 11-12