## What is a Triangle:

`A polygon with 3 edges,`

3 vertices, 3 angles.

We take 3 points and connect them with 3 sides below denoted as ΔPQR:

## Properties of a Triangle:

Sum of the three interior angles = 180°

Sum of the 2 sides > 3rd side

A triangle with vertices (points) P, Q, R:

is denoted as ΔPQR

## Area of a Triangle

With base b and height h:

A = 1/2bh

## Acute Triangle:

All 3 angles measure less than 90°

## Right Triangle:

Has one angle measuring 90° (right)

The other two angles < 90°

## Obtuse Triangle:

Has only one angle measuring > 90°

Obtuse angle is opposite the long side

## Scalene Triangle

No Sides Are Equal

## Isosceles Triangle

2 sides Are Equal

## Equilateral Triangle

All 3 sides are equal

### How does the Triangles Calculator work?

Free Triangles Calculator - This lesson walks you through the basics of a triangle and shows you triangle types like acute, right, obtuse, scalene, isosceles, equilateral.

### What 2 formulas are used for the Triangles Calculator?

Triangle PQR is written as ΔPQR

The sum of the three interior angles of a triangle equals 180°

For more math formulas, check out our

Formula Dossier
### What 7 concepts are covered in the Triangles Calculator?

- acute triangle
- A triangle for which all interior angles are acute.
- equilateral triangle
- A triangle with 3 equal sides
- isosceles triangle
- A triangle with two equal sides and an unequal third side
- obtuse triangle
- A triangle which has an obtuse angle as one of its interior angles.
- right triangle
- triangle in which one angle is a right angle
- scalene triangle
- a triangle with three unequal sides
- triangle
- a flat geometric figure that has three sides and three angles

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