Right angles are those ones that are produced by the intersection between two perpendicular lines. Furthermore, the measurement of an angle like this is of 90°.
Respect to the case of angles ∠1 and ∠4 in the attached image, you take into account that angles that are opposed between them, and one is inside the secant line and the other is outside a secant lines, in such a way that these angles are equal (ac you can notice in the picture), these angles are known as vertical angles. This angles are made by intersectinglines.
