Question

The transformation (x,y) -> (y,-x) is what degree rotation for a counter-clockwise turn?

Answer 1

270°

Explanation:

For example,

(x, y) is in 1st quadrant (x- coordinate is positive, y - coordinate is positive) , then

(y, - x) is in 4th (x- coordinate is positive, y - coordinate is negative).

x and y changed places, so clockwise is 90°,

and counter-clockwise 360-90= 270°.