Question

Use the graph to answer the question.

graph of triangle ABC with vertices at negative 2 comma negative 7, 3 comma negative 2, 2 comma negative 10 and a second triangle A prime, B prime C prime with vertices at 7 comma negative 2, 2 comma 3, 10 comma 2

Determine the direction and degree of rotation used to create the image.

90° counterclockwise rotation
270° counterclockwise rotation
90° clockwise rotation
180° clockwise rotation

Answer 1

(a) 90° CCW

Explanation:

You want the direction and degree of rotation that map ∆ABC to ∆A'B'C', given A(-2, -7) and A'(7, -2).

Graph

It is clear from the attached graph that the figure is rotated 90° counterclockwise, choice A.

Coordinates

The coordinates can give you a clue, as well. When we consider the rotation of point A to point A', we can look at it like this:

A(-2, -7) ⇒ A'(7, -2)

(x, y) ⇒ (-y, x) . . . . . . . . . . . rotation 90°CCW

The x-coordinate is now +7. Previously the y-coordinate was -7. Movement from -7 on the y-axis to +7 on the x-axis is a rotation 90° CCW.

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