If they're the same, then they are congruent. If they're on an image, you can use angles in parallel lines, such as Z (alternate) angles, F (corresponding) angles, or vertically opposite angles to show that they are equal. I hope this helps! Let me know if you need further explanation :)
When two lines intersect to make an x, angles on opposite sides of the X are called vertical angle. and both angles are equal, give me a second and i will give you an example.
