What transformation is represented by the rule (x, y)→(x, −y) ?

rotation of 180° about the origin

reflection across the x-axis

rotation of 90° counterclockwise about the origin

reflection across the y-axis

1 Answer
Sep 11, 2016

Reflection across the x-axis.


Use #color(blue)"squared paper"# and plot some coordinate points.

For example.

: #(2,3)" and " (-3,-2)" and reflect them in the x-axis."#

You should obtain the following results.

#(2,-3)" and " (-3,2)" respectively"#

Note that the x-coordinate remains unchanged, while the y-coordinate is the negative of the original point.

In general this can be expressed as

Under reflection in the x-axis #(x,y)to(x,-y)#