Math Problem Statement

The two adjacent vertices of a parallelogram ABCD are A(-4, -2) and B(1, -2). If the diagonals of the parallelogram intersect at the point M(1/2, 0), then find the other two vertices of the parallelogram.

Solution

Let's solve the first question (33) from the image.

Problem 33: Parallelogram with vertices

Given:

  • Adjacent vertices of parallelogram ABCDABCD are A(4,2)A(-4, -2) and B(1,2)B(1, -2).
  • The diagonals of the parallelogram intersect at point M(12,0)M\left(\frac{1}{2}, 0\right).

We are required to find the other two vertices of the parallelogram.

Key Concept:

  • The diagonals of a parallelogram bisect each other, meaning the midpoint of both diagonals is the same. Therefore, the midpoint of diagonal ACAC is equal to the midpoint of diagonal BDBD, which is given as M(12,0)M \left(\frac{1}{2}, 0\right).

Step 1: Find vertex CC

The midpoint of diagonal ACAC can be calculated as: MAC=(xC+xA2,yC+yA2)M_{AC} = \left( \frac{x_C + x_A}{2}, \frac{y_C + y_A}{2} \right) Since A(4,2)A(-4, -2) and M(12,0)M \left(\frac{1}{2}, 0\right), we equate the midpoint formula to MM's coordinates: (xC42,yC22)=(12,0)\left( \frac{x_C - 4}{2}, \frac{y_C - 2}{2} \right) = \left( \frac{1}{2}, 0 \right) From the first equation: xC42=12xC4=1xC=5\frac{x_C - 4}{2} = \frac{1}{2} \quad \Rightarrow \quad x_C - 4 = 1 \quad \Rightarrow \quad x_C = 5 From the second equation: yC22=0yC2=0yC=2\frac{y_C - 2}{2} = 0 \quad \Rightarrow \quad y_C - 2 = 0 \quad \Rightarrow \quad y_C = 2 Thus, vertex C(5,2)C(5, 2).

Step 2: Find vertex DD

Similarly, for diagonal BDBD, the midpoint is: MBD=(xD+xB2,yD+yB2)M_{BD} = \left( \frac{x_D + x_B}{2}, \frac{y_D + y_B}{2} \right) Substitute B(1,2)B(1, -2) and M(12,0)M \left(\frac{1}{2}, 0\right): (xD+12,yD22)=(12,0)\left( \frac{x_D + 1}{2}, \frac{y_D - 2}{2} \right) = \left( \frac{1}{2}, 0 \right) From the first equation: xD+12=12xD+1=1xD=0\frac{x_D + 1}{2} = \frac{1}{2} \quad \Rightarrow \quad x_D + 1 = 1 \quad \Rightarrow \quad x_D = 0 From the second equation: yD22=0yD2=0yD=2\frac{y_D - 2}{2} = 0 \quad \Rightarrow \quad y_D - 2 = 0 \quad \Rightarrow \quad y_D = 2 Thus, vertex D(0,2)D(0, 2).

Final Answer:

The coordinates of the other two vertices of the parallelogram are:

  • C(5,2)C(5, 2)
  • D(0,2)D(0, 2)

Would you like a detailed explanation for any other question or specific step?


Here are five related questions for further practice:

  1. If the diagonals of a parallelogram bisect each other, what other properties can you deduce about its angles?
  2. How do you find the length of the diagonals in a parallelogram if all vertices are given?
  3. If a parallelogram has two vertices on the x-axis, what special conditions hold for the vertices on the opposite diagonal?
  4. How can you determine whether a quadrilateral is a parallelogram given only its vertex coordinates?
  5. What formula do you use to calculate the area of a parallelogram given its vertices?

Tip: Remember that the diagonals of a parallelogram always bisect each other, which is a key property in many geometric proofs.

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Parallelogram Properties

Formulas

Midpoint formula: M(x, y) = [(x1 + x2)/2, (y1 + y2)/2]
Properties of diagonals in a parallelogram: Diagonals bisect each other

Theorems

Diagonal bisection theorem in parallelograms

Suitable Grade Level

Grade 10