Question

reflect △def across the y - axis. then rotate △def 90° counterclockwise around the origin. what are the coordinates of the vertices of △def? show your work.

Explanation:

Step1: Find coordinates of △DEF

Assume coordinates of D(-1, 3), E(-1, 0), F(-5, 0).

Step2: Reflect across y - axis

The rule for reflecting a point (x,y) across the y - axis is (-x,y).
For D(-1, 3), D'=(1, 3); for E(-1, 0), E'=(1, 0); for F(-5, 0), F'=(5, 0).

Step3: Rotate 90° counter - clockwise around origin

The rule for rotating a point (x,y) 90° counter - clockwise around the origin is (-y,x).
For D'(1, 3), D''=(-3, 1); for E'(1, 0), E''=(0, 1); for F'(5, 0), F''=(0, 5).

Answer:

D''(-3, 1), E''(0, 1), F''(0, 5)