Math Problem Statement

The figure shows triangle ABC plotted on a coordinate plane. The triangle is first rotated by 90° counterclockwise about the origin and then reflected about the line y = -x. Which graph shows the transformed triangle?

Solution

Let's solve the problem step by step.

Step 1: Rotation by 90° Counterclockwise

To rotate a point (x,y)(x, y) by 90° counterclockwise around the origin, the new coordinates (x,y)(x', y') are given by: (x,y)=(y,x)(x', y') = (-y, x) We need to apply this transformation to the vertices of triangle ΔABC\Delta ABC.

  • Point A is at (1,2)(-1, 2). After rotation: A=(2,1)A' = (-2, -1)
  • Point B is at (1,3)(1, -3). After rotation: B=(3,1)B' = (3, 1)
  • Point C is at (4,2)(4, 2). After rotation: C=(2,4)C' = (-2, 4)

Step 2: Reflection Over the Line y=xy = -x

The reflection of a point (x,y)(x, y) over the line y=xy = -x is given by swapping and negating the coordinates: (x,y)=(y,x)(x', y') = (-y, -x) Now, apply this transformation to the new vertices A,B,CA', B', C'.

  • Point A' is at (2,1)(-2, -1). After reflection: A=(1,2)A'' = (1, 2)
  • Point B' is at (3,1)(3, 1). After reflection: B=(1,3)B'' = (-1, -3)
  • Point C' is at (2,4)(-2, 4). After reflection: C=(4,2)C'' = (-4, 2)

Final Coordinates of the Transformed Triangle

The new vertices of the transformed triangle are:

  • A=(1,2)A'' = (1, 2)
  • B=(1,3)B'' = (-1, -3)
  • C=(4,2)C'' = (-4, 2)

By checking these points on the coordinate plane, the transformed triangle can be graphed.

Would you like to see further details or explanations?

Here are five questions to expand your understanding:

  1. How would the transformation change if the triangle was rotated by 180° instead of 90°?
  2. What happens when you reflect a shape over the line y=xy = x instead of y=xy = -x?
  3. How would the transformation rules change if you reflected over the x-axis?
  4. What would happen if the rotation was clockwise instead of counterclockwise?
  5. Can you describe the combined transformation as a single matrix operation?

Tip: Remember that combining transformations (like rotation and reflection) can often be simplified by using matrices, which makes it easier to apply multiple transformations at once.

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Math Problem Analysis

Mathematical Concepts

Geometry
Transformations
Rotation
Reflection

Formulas

Rotation of a point (x, y) by 90° counterclockwise: (x', y') = (-y, x)
Reflection of a point (x, y) over the line y = -x: (x', y') = (-y, -x)

Theorems

Transformation Theorems

Suitable Grade Level

Grades 8-10