Question

Which of the following is the rule for rotating the point with coordinates (x,y), 90 counterclockwise about the origin? A. (x,y)→(−y,x) B. (x,y)→(y,x) C. (x,y)→(x,−y) D. (x,y)→(y,−x)

Answer 1

Answer: A. (x,y)→(−y,x)

Explanation:

For rotating a point about the origin at 90° in the counterclockwise direction, the x and y coordinate values are interchanged with the interchanged y value also given a negative sign.

For clarity :

Given the coordinate (2, 5)

Rotating (2, 5) about the origin at an angle of 90° in the counterclockwise direction:

(x, y) - - - - - - - - - - > (-y, x)

(2, 5) - - - - - - - - - - - > (-5, 2)