Which of the following sequences of transformations maps
Figure 1 to Figure 2?
90° clockwise rotation around
the origin, then a reflection
across the x-axis
90° counterclockwise rotation
around the origin, then a
reflection across the x-axis
-4
reflection across the y-axis, then
a reflection across the x-axis
reflection across the x-axis, then
a reflection across the y-axis

Which of the following sequences of transformations maps Figure 1 to Figure 2 90 clockwise rotation around the origin then a reflection across the xaxis 90 coun class=

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Answer:

  • First choice: 90° clockwise rotation around the origin, then a reflection across the x-axis.

Explanation:

The vertices of the figure 1 are:

  • (-3, 2)
  • (-4, 5)
  • (-3, 8)
  • (-7,5)

The vertices of figure 2 are:

  • (2, -3)
  • (5, -4)
  • (8, -3)
  • (5, -7)

By simple inspection, you can tell that if you rotate the figure 1 90º clockwise and then reflect the image across the x-axys you obtain the figure 2.

You can prove that analitically.

1. Rotation 90º clockwise

A 90º clockwise reotation is the same that a 270º counterclockwise rotation and the mathematical rule for this is:

  • (x,y) → (y, x)

Applying that rule to the vertices of figure 1, you obtain:

  • (-3, 2) → (2, 3)
  • (-4, 5) → (5, 4)
  • (-3, 8) → (8, 3)
  • (-7,5) → (5, 7)

2. Reflection across the x-axis.

A reflection across the x-axis keeps the same x-coordinate and changes the sign of the y-coordinate. The rule is:

  • (x,y) → (x, -y)

Applying that rule to the previous points yields to:

  • (2, 3) → (2, -3)
  • (5, 4) → (5, -4)
  • (8, 3) → (8, -3)
  • (5, 7) → (5, -7)

Which are the coordinates of the figure 2. Thus, you have proved that the sequence of transformations 90° clockwise rotation around the origin, then a reflection across the x-axis (first choice) maps the figure 1 to figure 2.

Answer:

First choice: 90° clockwise rotation around the origin, then a reflection across the x-axis.

Step-by-step explanation: