Math Problem Statement

A figure was transformed on a coordinate grid using the rule (x,y)→(−x,−y) .

Which of the following describes the transformation? A.A 90∘ clockwise rotation about the origin. B.A 180∘ clockwise about the origin. C.A reflection across the x –axis. D.A reflection across the y –axis.

Solution

The transformation rule (x,y)(x,y)(x, y) \to (-x, -y) means that each point of the figure is transformed into its opposite in both the xx- and yy-directions. This corresponds to rotating the figure 180180^\circ about the origin.

Explanation:

  • A 180180^\circ rotation about the origin flips each point directly across the origin. For instance:
    • The point (a,b)(a, b) becomes (a,b)(-a, -b).
    • The point (a,b)(-a, -b) becomes (a,b)(a, b).

None of the other options are correct:

  • A 9090^\circ rotation clockwise: This would map (x,y)(x, y) to (y,x)(y, -x), which is different.
  • Reflection across the xx-axis: This maps (x,y)(x, y) to (x,y)(x, -y), which does not match the rule.
  • Reflection across the yy-axis: This maps (x,y)(x, y) to (x,y)(-x, y), which also does not match the rule.

Correct Answer:

B. A 180180^\circ clockwise rotation about the origin.


Do you want further clarification or a diagram for this transformation?

Related Questions:

  1. What is the difference between rotation and reflection in geometry?
  2. How can we use transformation rules to identify reflections?
  3. What happens when you apply the rule (x,y)(x,y)(x, y) \to (-x, -y) twice to a point?
  4. How can coordinate rules help in predicting compositions of transformations?
  5. Can you describe transformations that result from other angles of rotation (90,27090^\circ, 270^\circ)?

Tip:

When identifying transformations, always test the rule on specific points to understand its effect on the figure.

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Transformations
Rotations

Formulas

(x, y) → (−x, −y)

Theorems

Rotation Theorem for 180° about the Origin

Suitable Grade Level

Grades 8-10