Question

Indicate which pairs of angles are: Vertically opposite angles.

Answer 1

Concept of vertically opposite angles:

When two lines intersect at a vertex, the vertically opposite angles are equal.

In the given figure, angles $\angle 1\&\angle 4$ are vertically opposite angles.

and also angles $\angle 2+\angle 3=\angle 5$ because they are vertically opposite angles.

Hence, $\angle 1\&\angle 4$ and $\angle 2+\angle 3\&\angle 5$ are the two pairs of vertically opposite angles.