Question

what is the rule for a counterclockwise rotation of 270° about the origin?
○ a. f(x, y) = (-y, x)
○ b. f(x, y) = (y, -x)
○ c. f(x, y) = (y, x)
○ d. f(x, y) = (-x, y)

Explanation:

Step1: Recall rotation rules

Rotation rules about the origin:

• A \(90^{\circ}\) counter - clockwise rotation: \(f(x,y)=(-y,x)\)
• A \(180^{\circ}\) counter - clockwise rotation: \(f(x,y)=(-x,-y)\)
• A \(270^{\circ}\) counter - clockwise rotation: \(f(x,y)=(y, -x)\)

Answer:

B. \(f(x,y)=(y, -x)\)