Geometry Homework

Question

Help!

If triangle JKL is rotated 90 degrees counterclockwise about the origin, what are the coordinates of K?

Points of triangle JKL : (3,4), (1,2), (5,1)

A. (4,3)

B. (-4,3)

C. (-3,4)

D. (-3,-4)

Answer 1

To rotate a point about the origin 90 degrees counter-clockwise in (x,y) you switch the x and y coordinates and then change the sign of the new x coordinate.

Ex.

(6,3) -> Switch x and y -> (3,6) -> Change the sign of the new x -> (-3,6)

Another 90 degrees would be (-6,-3) and then another 90 degrees would be (3, -6). A further 90 degrees would return us to the point (6,3)

Assuming that point K is at (3,4):

(3,4) -> Switch x and y -> (4,3) -> Change the sign of the new x -> (-4,3)