Math Problem Statement

Координаты вершин пирамиды: A(3, 3, 5), B(1, 1, -1), C(-3, 3, 2), D(1, 1, 0). Найдите уравнение грани ABC. Определите расстояние от вершины D до этой грани — длину высоты h_D пирамиды.

Solution

This problem involves analyzing a pyramid with given vertices, solving for the equation of a plane defined by three of its vertices, and determining the height of the pyramid from the fourth vertex to that plane. Here's how we can approach the solution:

Given:

  • Vertices of the pyramid:
    • A(3,3,5)A(3, 3, 5)
    • B(1,1,1)B(1, 1, -1)
    • C(3,3,2)C(-3, 3, 2)
    • D(1,1,0)D(1, 1, 0)

We need to:

  1. Find the equation of the plane containing points AA, BB, and CC.
  2. Compute the perpendicular distance from point DD to this plane, which will be the height hDh_D of the pyramid.

Step 1: Find the equation of the plane ABC\text{ABC}

The general equation of a plane is: ax+by+cz+d=0ax + by + cz + d = 0 We need to find aa, bb, cc, and dd.

  1. Determine the normal vector to the plane: Use two vectors lying on the plane: AB=(BxAx,ByAy,BzAz)=(13,13,15)=(2,2,6)\vec{AB} = (B_x - A_x, B_y - A_y, B_z - A_z) = (1 - 3, 1 - 3, -1 - 5) = (-2, -2, -6) AC=(CxAx,CyAy,CzAz)=(33,33,25)=(6,0,3)\vec{AC} = (C_x - A_x, C_y - A_y, C_z - A_z) = (-3 - 3, 3 - 3, 2 - 5) = (-6, 0, -3) The cross product AB×AC\vec{AB} \times \vec{AC} gives the normal vector: \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ -2 & -2 & -6 \\ -6 & 0 & -3 \end{vmatrix}$$ Expand the determinant: $$\vec{n} = \mathbf{i}((-2)(-3) - (-6)(0)) - \mathbf{j}((-2)(-3) - (-6)(-6)) + \mathbf{k}((-2)(0) - (-6)(-2))$$ $$\vec{n} = \mathbf{i}(6) - \mathbf{j}(18 - 36) + \mathbf{k}(-12)$$ $$\vec{n} = (6, -18, -12)$$ Simplify: $$\vec{n} = (1, -3, -2) \quad \text{(dividing by the GCD 6)}.$$
  2. Plane equation: Substitute (1,3,2)(1, -3, -2) as (a,b,c)(a, b, c), and use point A(3,3,5)A(3, 3, 5) to solve for dd: 1(x)3(y)2(z)+d=01(x) - 3(y) - 2(z) + d = 0 Substitute A(3,3,5)A(3, 3, 5): 1(3)3(3)2(5)+d=01(3) - 3(3) - 2(5) + d = 0 3910+d=03 - 9 - 10 + d = 0 d=16d = 16 The equation of the plane is: x3y2z+16=0x - 3y - 2z + 16 = 0

Step 2: Distance from D(1,1,0)D(1, 1, 0) to the plane

The distance from a point (x1,y1,z1)(x_1, y_1, z_1) to a plane ax+by+cz+d=0ax + by + cz + d = 0 is given by: Distance=ax1+by1+cz1+da2+b2+c2\text{Distance} = \frac{|a x_1 + b y_1 + c z_1 + d|}{\sqrt{a^2 + b^2 + c^2}} Substitute D(1,1,0)D(1, 1, 0), a=1a = 1, b=3b = -3, c=2c = -2, d=16d = 16: Distance=1(1)3(1)2(0)+1612+(3)2+(2)2\text{Distance} = \frac{|1(1) - 3(1) - 2(0) + 16|}{\sqrt{1^2 + (-3)^2 + (-2)^2}} Distance=13+0+161+9+4\text{Distance} = \frac{|1 - 3 + 0 + 16|}{\sqrt{1 + 9 + 4}} Distance=1414\text{Distance} = \frac{|14|}{\sqrt{14}} Distance=14\text{Distance} = \sqrt{14}

Thus, the height hDh_D of the pyramid is 14\sqrt{14}.


Final Answer:

  1. Equation of the plane ABC\text{ABC}: x3y2z+16=0x - 3y - 2z + 16 = 0
  2. Height of the pyramid hDh_D: 14\sqrt{14}

Would you like further clarification or a step-by-step breakdown of any part?

Here are five related questions:

  1. How do you calculate the volume of the pyramid using this height?
  2. How can we determine if a point lies on the plane?
  3. What are alternative methods to find the normal vector of a plane?
  4. How can the cross-product magnitude help determine the area of a triangle on a plane?
  5. How would you rewrite the plane equation if the GCD were not used?

Tip: Always verify your cross-product calculations to avoid errors in determining the normal vector.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Plane Equations
Distance from Point to Plane

Formulas

Equation of a plane: ax + by + cz + d = 0
Distance from point to plane: |ax1 + by1 + cz1 + d| / √(a² + b² + c²)

Theorems

Equation of a plane through three points
Distance formula from a point to a plane

Suitable Grade Level

Grades 9-12