# Types of triangles ## Contents

• 1 triangle
• 2 types of triangles
• 3 angles of triangles
• 4 The area of ​​triangles
• 5 Circle the triangles
• 6 References

## The triangle

A triangle is defined as a closed form , all its points are connected, and it contains three straight lines.  , and the triangle is named relative to the names of the points of its heads, so if the names of the triangle heads are head A, head B, and head C, then the triangle is named ABC, and so on. 

## Types of triangles

There are various types of triangles. Here are some basic types of triangles: 
• Acute trianlges: Acute trianlges can be defined as triangles whose three angles are less than 90 °, for example: acute triangle a b c, angle a b c measure equals 78 degrees, and the angle b c measure is equal to 34 degrees, and the angle measure GBA equals 68 degrees.
• Obtuse triangles: The angle triangles can be defined as triangles in which one angle measure is greater than 90 degrees, for example the triangle A B C, the angle measure A B C equals 40 degrees, and the angle measure B C A Equal to 19 degrees, and the angle measure GBA equals 121 degrees.
• Triangles corner ( in English: Right triangles): can be defined triangles corner as triangles where measuring one angle equal to 90 degrees, for example , the triangle A B C, measuring the angle A B C is equal to 90 degrees, and angle measurement B C A is equal to 17 degrees, and the angle measure GBA equals 73 degrees.
• Triangles equal ribs ( in English: Equilateral triangles): can be defined equilateral triangles as triangles where the lengths of the three sides are equal be, for the triangle example a b c, the length of the rib A B is equal to 1.85 cm, and the length of the rib b c is equal to 1.85 cm, and the length of The side c is equal to 1.85 cm.
• Triangles equal legs ( in English: Isosceles triangles): can be defined as triangles equal legs as triangles where the length of one of her legs are equal, for the triangle example a b c, the length of the rib A B is equal to 1.77 cm, and the length of the rib b c is equal to 1.77 cm.
• Scalene triangles: Scalene triangles can be defined as triangles in which the lengths of all three sides are different, for example triangle ABC , the length of the side AB is equal to 1.42 cm, the length of the side B is equal to 2.5 cm, and the length of the The side c is equal to 2.08 cm.

## The angles of the triangles

The sum of the three angles of the inner triangle must always be equal to 180 degrees, for example: the triangle ABC, the measure of its angle ABC equals 41 degrees, the measurement of the angle BCA equals 71 degrees, and the measurement of the angle CAB equals 68 degrees , Since the sum of these three angles is equal to 180 degrees, and so on in all triangles. 

## The area of ​​the triangles

The area of ​​the triangles can be calculated by multiplying the length of the base by the height of the triangle and multiplying by the number 0.5, and the law of the area of ​​the triangle can be summarized if the area is m, the length of the base l, and the height is p, then the law of the area of ​​the triangle (m = 0.5 * l * p), for example Example: A triangle with a base length of 15 cm, and a height of 4 cm, its area will be (m = 0.5 * 15 * 4) and equal to 30 cm 2 . 

## Surrounding triangles

The circumference of the triangle can be defined as the sum of the lengths of its three sides, so if we denote the circumference of the symbol h, the length of the first side a b, the length of the second side b c, and the length of the third side c a, the law of the triangle will be (h = a b + b c + + C d), for example: if we want to calculate the circumference of a triangle whose first side length is 7 cm, the length of its second side equals 9 cm, and the length of its third side equals 12 cm, then the circumference of the triangle will be the sum of the lengths of its sides (h = 7 +9 + 12 It equals 28 cm.