Math Problem Statement

Triangle A is transformed by the combined transformation of a rotation of 180° about the point (-2,0) followed by a translation with vector (-3) 2

One point on triangle A is invariant under the combined transformation.

Find the coordinates of this point.

Solution

To find the invariant point under the combined transformation, follow these steps:

Step 1: Define the Transformations

  1. Rotation of 180° about (-2,0)
    The formula for rotating a point (x,y)(x, y) by 180° about (h,k)(h, k) is:
    (x,y)=(2hx,2ky)(x', y') = (2h - x, 2k - y) Substituting h=2h = -2 and k=0k = 0, we get:
    (x,y)=(4x,y)(x', y') = (-4 - x, -y)

  2. Translation by (32)\begin{pmatrix} -3 \\ 2 \end{pmatrix}
    This means shifting the coordinates as:
    (x,y)=(x3,y+2)(x'', y'') = (x' - 3, y' + 2)

Step 2: Find the Invariant Point

An invariant point remains unchanged after both transformations. That means:
(x,y)=(x,y)(x, y) = (x'', y'') Substituting the transformations:

(x,y)=(4x3,y+2)(x, y) = (-4 - x - 3, -y + 2)

This gives the equations:

  1. x=4x3x = -4 - x - 3
    x+x=7x + x = -7 2x=7x=722x = -7 \Rightarrow x = -\frac{7}{2}

  2. y=y+2y = -y + 2
    y+y=2y + y = 2 2y=2y=12y = 2 \Rightarrow y = 1

Final Answer:

The invariant point is (72,1)\left(-\frac{7}{2}, 1 \right).


Do you want more details or have any questions?

Here are some related questions:

  1. How do you find the center of rotation for a given transformation?
  2. What are the properties of a 180° rotation transformation?
  3. How do you determine if a transformation has an invariant point?
  4. What are other transformations that might leave a point unchanged?
  5. How does a 90° rotation differ from a 180° rotation?

Tip:

Always check for invariant points in reflection, rotation, and translation by solving for points that satisfy the equation (x,y)=(x,y)(x, y) = (x'', y'').

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Math Problem Analysis

Mathematical Concepts

Geometry
Rotation
Translation
Coordinate Geometry

Formulas

Rotation formula for 180° about (h, k): (x', y') = (2h - x, 2k - y)
Translation formula: (x'', y'') = (x' - 3, y' + 2)

Theorems

Invariant point under combined transformations

Suitable Grade Level

Grades 9-11