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# Triangles: Types of Triangles A closed structure formed by three intersecting lines is described as a triangle. A triangle has three sides, three angles, and three vertices A, B, and C. A triangle is a polygon with all these properties. The three angles of a triangle always sum equal to 180°. For example: In triangles ABC, denoted as ABC. AB,BC and CA are the three sides. AB , BC , CA are three angles. A, B, and C are three vertices ABC= AB + BC + CA ABC= 600 + 60 + 60 ABC= 1800

## Types of Triangles

There are basically six types of triangle, which is below.

1. Isosceles Triangle
2. Equilateral Triangle
3. Scalene Triangle
4. Right-angled Triangle
5. Obtuse Triangle
6. Acute-angled Triangle

### 1.Isosceles Triangles In this triangle only two sides are equal and two angles are equal.

### 2.Equilateral Triangle In equilateral, all three sides are equal(AB=BC=CA) and all three angles are equal ( AB = BC = CA=600)

### 3. Scalene Triangle In this type of triangle, there are no sides equal and no equal angles.

### 4.Right Triangle In the right triangle, one angle always 90°.

### 5.Obtuse Triangle In this type of triangle One angle > 90° or more than 90°.

### 6. Acute Triangle All angles < 90°.

## Area of Triangle The area is 1/2 of the base times height.

“b” is the distance along the base
“h” is the height

Area = ½ × b × h

This formula works for all types of triangles.

### Example: What is the area of a triangle? (Note: 100 is the height, not the length of the left-hand side)

Height = h = 100

Base = b = 40

Area = ½ × b × h

Area = ½ ×40 × 100 = 2000

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