In Geometry, a triangle is the most important shape, defined as a double closed drawing consisting of 3 sides, 3 angles, and 3 vertices. In simple terms, a triangle is a polygon with 3 sides. The word triangle is derived from the Latin word 'triangulus,' meaning three chambers.

In ancient times, astronomers developed a method called triangles to determine the distances of distant stars. They measure the distance from two different points, and then measure the angle of shift or parallax, which is formed by the movement of the observer between the two points. Then use the law of sin to calculate the required distance.

The Egyptians created the pyramids about the year 2900 B.C. Its shape is actually that of a 3D tower, with a triangular face. It is a perfectly designed model that its length and angles on all sides are the same. Miletus (624 BC – 547 BC), a Greek mathematician, adopted the Egyptian Geometry and was brought to Greece.

Aristarchus (310 BC – 250 BC), a Greek mathematician, used the above method to calculate the distance between the Earth and the Moon. Eratosthenes (276 BC – 195 BC), too, used a similar method to find the distance around the earth's surface (called the orbit).

This article will discuss the meaning of a triangle, the various types of triangles and their structures, and their actual use.

A triangle has two closed sides with 3 sides. It is a triangular polygon, three vertices, and three combined angles that form a closed drawing. We use the ∆ symbol to show the triangle