Reflection Math Example 2

Follow the full solution, then compare it with the other examples linked below.

Example 2

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Reflect the point Q(โˆ’2,5)Q(-2, 5) over the line y=xy = x. Find the image.

Solution

  1. 1
    Step 1: The rule for reflection over the line y=xy = x is (x,y)โ†’(y,x)(x, y) \to (y, x) โ€” swap the coordinates.
  2. 2
    Step 2: Apply to Q(โˆ’2,5)Q(-2, 5): Qโ€ฒ=(5,โˆ’2)Q' = (5, -2).
  3. 3
    Step 3: Verify: the midpoint of QQ and Qโ€ฒQ' should lie on y=xy=x. Midpoint =(โˆ’2+52,5+(โˆ’2)2)=(1.5,1.5)= \left(\tfrac{-2+5}{2}, \tfrac{5+(-2)}{2}\right) = (1.5, 1.5). On y=xy=x? Yes. โœ“

Answer

Qโ€ฒ=(5,โˆ’2)Q' = (5, -2)
Reflecting over y=xy=x swaps the x and y coordinates. The line y=xy=x is the axis of reflection, and the midpoint of any point and its image always lies on this axis. This reflection is its own inverse โ€” applying it twice returns to the original point.

About Reflection

A rigid transformation that flips a figure over a line (the mirror line), producing a mirror image.

Learn more about Reflection โ†’

More Reflection Examples