### Video Transcript

Five points are plotted on the
grid in the figure below. When reflecting point π across
the dotted line, which of the four other points will it map onto? Is it option (A) point π,
option (B) point π, (C) point π, or (D) point π
?

Remember, a reflection is a
transformation that preserves the perpendicular distances of all points from the
mirror line. In particular, if we define the
image of π to be the point π prime, this is the reflection through the mirror
line where the mirror line is the perpendicular bisector of the line segment
that joins these points.

So, we can find the image of π
by drawing a line perpendicular to the mirror line. Thatβs the dotted line in this
picture. When we do, we see that this
perpendicular line passes through point π
. In particular, point π
is the
same perpendicular distance from the dotted line as point π. So, the correct answer is
option (D). Point π
is the image of π in
a reflection through the dotted line.