Question

Given a triangle JLM with vertices J(-4,3), L(-2,7), and M(2,7). What would the coordinates be if it was reflected across the line y=1?

Answer 1

Answer: M'(2, - 5), L'(-2, -5), j'(-4, - 1)

Explanation:

When we do a reflection over a given line, the distance between all the points (measured perpendicularly to the line) does not change.

The line is y = 1.

Notice that a reflection over a line y = a (for any real value a) only changes the value of the variable y.

Let's reflect the points:

J(-4, 3)

The distance between 3 and 1 is:

D = 3 - 1 = 2.

Then the new value of y must also be at a distance 2 of the line y = 1

1 - 2 = 1

The new point is:

j'(-4, - 1)

L(-2, 7)

The distance between 7 and 1 is:

7 - 1 = 6.

The new value of y will be:

1 - 6 = -5

The new point is:

L'(-2, -5)

M(2,7)

Same as above, the new point will be:

M'(2, - 5)