Angle facts

Sum of angles connected to a line from the one side = 180 degrees.

Sum of angles in any triangle = 180 degrees.

Sum of the two smaller angles in a right-angled triangle = 90 degrees.

When a line crosses parallel lines alternate angles are equal and corresponding angles are equal.
When two lines cross, opposite angles are equal.

If in a triangle all sides equal, the angles are all 60 degrees.