1. Do the angles of a cyclic quadrilateral add up to 360o?
The interior angles of all quadrilaterals add up to 360o.
2. If the opposite angles of a quadrilateral add up to 180o does the quadrilateral have to be cyclic?
Yes, a circle can be drawn through the vertices of all such quadrilaterals
3. Is a square a cyclic quadrilateral?
Yes, because its opposite angles add up to 180o (90o + 90o)
