Picture to the Question

Reflect across segment AB, and across AC.

Step-by-step explanation:

Reflecting the triangle across segment AB will move triangle ABC onto DBA, and reflecting it over AC will move triangle ABC onto AEC. Showing that they have the same angles.

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.