Math Problem Statement

The points have co-ordinates A(–1, 6) B(3, 2) and C(–5, –6). Given that D and E are the midpoint of AB and AC respectively, calculate the midpoint of DE and the length of DE.

Solution

To solve the problem:

Step 1: Calculate the midpoints of ABAB and ACAC

The midpoint formula is: Midpoint=(x1+x22,y1+y22)\text{Midpoint} = \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right)

Midpoint DD of ABAB:

D=(1+32,6+22)=(1,4)D = \left( \frac{-1 + 3}{2}, \frac{6 + 2}{2} \right) = \left( 1, 4 \right)

Midpoint EE of ACAC:

E=(1+(5)2,6+(6)2)=(3,0)E = \left( \frac{-1 + (-5)}{2}, \frac{6 + (-6)}{2} \right) = \left( -3, 0 \right)

Step 2: Calculate the midpoint of DEDE

Using the midpoint formula again: Midpoint of DE=(xD+xE2,yD+yE2)\text{Midpoint of } DE = \left( \frac{x_D + x_E}{2}, \frac{y_D + y_E}{2} \right) Midpoint of DE=(1+(3)2,4+02)=(1,2)\text{Midpoint of } DE = \left( \frac{1 + (-3)}{2}, \frac{4 + 0}{2} \right) = \left( -1, 2 \right)

Step 3: Calculate the length of DEDE

The distance formula is: Distance=(x2x1)2+(y2y1)2\text{Distance} = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} Substituting the coordinates of D(1,4)D(1, 4) and E(3,0)E(-3, 0): Length of DE=(31)2+(04)2=(4)2+(4)2=16+16=32=42\text{Length of } DE = \sqrt{(-3 - 1)^2 + (0 - 4)^2} = \sqrt{(-4)^2 + (-4)^2} = \sqrt{16 + 16} = \sqrt{32} = 4\sqrt{2}

Final Answer:

  1. The midpoint of DEDE is (1,2)(-1, 2).
  2. The length of DEDE is 424\sqrt{2}.

Would you like further clarification or a visualization? Here are 5 related questions to deepen your understanding:

  1. What would the length of DEDE be if A,B,A, B, or CC shifted coordinates?
  2. How does the midpoint formula differ when applied in three dimensions?
  3. What is the significance of the line DEDE in terms of the triangle's geometry?
  4. Can you verify the calculations by plotting the points on a graph?
  5. How is the distance formula derived from the Pythagorean theorem?

Tip: Always label your axes and points when solving graphically to avoid confusion.

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Midpoint Formula
Distance Formula

Formulas

Midpoint formula: ( (x1 + x2)/2, (y1 + y2)/2 )
Distance formula: sqrt((x2 - x1)^2 + (y2 - y1)^2)

Theorems

Pythagorean Theorem (used in the distance formula)

Suitable Grade Level

Grades 9-11