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A triangle is a shape, or a part of two dimensional space. It has three straight sides and three vertices. The three angles of a triangle always add up to 180° (180 degrees). It is the polygon with the least possible number of sides. A triangle with vertices A, B, C is written as $\triangle ABC$ .^[1]^[2] The study of geometry related to triangles is called trigonometry. Modern computers usually use triangles to make more complex graphic images or shapes.

Types of triangles

This is an *isosceles right triangle*, because it has a right angle and two of its sides have the same length.

Triangles can be grouped according to how many of their sides are equal:^[3]

if all the three sides of a triangle have the same length, then it is an equilateral triangle.
if a triangle has two sides with the same length, then it is an isosceles triangle.
if all the three sides of a triangle have different lengths, then we have a scalene triangle.

Triangles can also be grouped by their angles:^[3]

if a triangle has a right angle, that is, if one of the angles of that triangle measures 90° (90 degrees), then it is a right triangle. The opposite side to the right angle is the hypotenuse.
if a triangle has an obtuse angle, that is, if one of the angles of that triangle is larger than 90°, then it is an obtuse triangle.
if a triangle has only acute angles, that is, if all the angles of that triangle are less than 90°, then it is an acute triangle.

Equilateral triangle
Isosceles triangle
Scalene triangle
Right Angled triangle
Obtuse Angled triangle
Acute Angled triangle

Area

The area of a triangle is equal to base times height times one half.

$area={\frac {base\times height}{2}}$

Related pages

References

↑ "List of Geometry and Trigonometry Symbols". Math Vault. 2020-04-17. Retrieved 2020-09-01.
↑ Weisstein, Eric W. "Triangle". mathworld.wolfram.com. Retrieved 2020-09-01.
↑ ^3.0 ^3.1 "Triangles - Equilateral, Isosceles and Scalene". www.mathsisfun.com. Retrieved 2020-09-01.