The sum of the lengths of the three sides gives the perimeter of triangles.The sum of lengths of any two sides of a triangle is more than the remaining side’s length.

A triangle has 3 sides, 3 angles, and 3 vertices.Here are a few basic properties of a triangle: Euclidean geometry and trigonometry make great use of the properties of triangles. Many mathematicians used it in solving their problems. The properties of triangles have a broad use. Scalene TriangleĪ scalene triangle is a triangle in which all the sides have different measures and all the interior angles are also different. Note that the angles of an equilateral triangle do not depend on the lengths of the sides. In an equilateral triangle, the sides AB = BC = AC and ∠ ABC =∠ ACB = ∠ BAC An equilateral triangle is sometimes referred to as an equiangular triangle because all three angles are equal. In this case, each interior angle of an equilateral triangle is 60 degrees. Equilateral triangleĪn equilateral triangle has all three sides equal, and all three interior angles equal, too. In the diagram above, the length of side AB = AC and ∠ ABC =∠ ACB. Equal lengths of a triangle are shown by making an arc on each side.

We can classify triangles into 3 types based on the lengths of their sides:Īn isosceles triangle is a triangle in which two sides and two angles are equal. Classification of triangles according to the length of their sides In the illustration above, angle a = 90 degrees while angles b and c are acute angles. The hypotenuse is the side of a right triangle with the longest length. Right TriangleĪ right triangle is a triangle in which one of the angles is exactly 90 degrees. Obtuse triangleĪn obtuse triangle is a triangle in which one of the interior angles is more than 90 degrees.Īngle a is more obtuse, while angles b and c are acute. The types of triangles are classified based on:Ĭlassification of triangles according to the measure of interior anglesĪccording to the measure of interior angles, we can classify triangles into three categories:Īn acute angle triangle is a triangle in which all three interior angles are less than 90 degrees.Įach one of the angles a, b and c is less than 90 degrees. We use the symbol ∆ to denote a triangle. It is a polygon with three corners, three vertices, and three angles joined together that forms a closed diagram. What is a Triangle?Ī triangle is a two-dimensional closed figure with 3 sides. This article will discuss the meaning of a triangle, the different types of triangles and their properties, and their real-life applications. Eratosthenes (276 BC – 195 BC), again, used the same method to determine the distance around the surface of Earth (called circumference). Miletus (624 BC – 547 BC), a Greek mathematician, adopted Egypt’s geometry and was brought to Greece.Īristarchus (310 BC – 250 BC), a Greek mathematician, used the above method to find the distance between the Earth and the Moon. It is a perfectly engineered model that its lengths and angles on all sides are the same. Its shape is actually that of a 3D pyramid, which has triangular faces. The Egyptians created the pyramids around 2900 B.C. Then they used to apply the law of sines for calculating the required distance. They measure the distance from two different locations, then measure the angle created by shift or parallax, formed by the observer’s movement between the two locations. The word triangle is taken from the Latin word ‘triangulus,’ which means three-cornered.ĭuring ancient times, astronomers had created a method called triangulation to determine the distances of the distant stars. In simple words, a triangle is a polygon with 3 sides. In Geometry, a triangle is the most important shape, defined as a closed two-dimensional diagram containing 3 sides, 3 angles, and 3 vertices. Types of Triangles – Explanation & Examples

Sample of scalene triangle