A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices A, B, and C is denoted \triangle ABC. In Euclidean geometry, any three points, when non-collinear, determine a unique triangle and simultaneously, a unique plane.What kind of triangle is ∆ ABC? A triangle which has all the three angles acute that is, less than 90°, is called an acute angled triangle or acute triangle. In other words, a triangle is which all the three angles are acute is called an acute-angled triangle. In the given figure ∠A, ∠B and ∠C are acute angle. Thus, ∆ABC is an acute-angled triangle.
