Question

Rotate ∆ABC by 90° clockwise, about the origin, and then reflect in the x-axis.

What are the coordinates of the new triangle?

Answer 1

A = (1, 1)

B = (3, 2)

C = (2, 4)

Explanation:

Vertices of the triangle:

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

Mapping rule for a 90° clockwise rotation about the origin:

(x, y) → (y, -x)

Therefore:

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

Mapping rule for a reflection in the x-axis:

(x, y) → (x, -y)

Therefore:

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

Therefore, the coordinates of the new triangle are:

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