1. What is a vertex of a triangle?
A vertex is a corner. A triangle has three vertices.
2. Is the longest side of a triangle always opposite the biggest angle?
Yes, and the SMALLEST angle is always opposite the SHORTEST side.
3. Can a triangle be both ISOSCELES and RIGHT-ANGLED?
Yes, its angles would be 90o, 45o and 45o.
4. Is a triangle a polygon?
Yes. It is the polygon with the smallest number of sides.