Back to Parallel lines are taken to parallel lines — Problem 4 · Task Set 21

Exercises: Rigid Motions Preserve Parallelism

Work through each section in order. Two lines are parallel when they have the same slope (or are both vertical). For each transformation, find the slopes of the image lines and check whether they stay equal.

Grade 8·20 problems·~30 min·Common Core Math - Grade 8·standard·8-g-a-1c

Work through problems with immediate feedback

Fluency Practice

$Two horizontal lines and their images after a 90-degree counterclockwise turn, shown as two dashed vertical lines$

The horizontal parallel lines $y = 2$ and $y = 5$ are rotated $90\degree$ counterclockwise about the origin. What are the image lines?

The vertical lines $x = -2$ and $x = -5$ , which are parallel

The lines cross, so they are no longer parallel

Still $y = 2$ and $y = 5$ , unchanged

One vertical and one horizontal line