Triangles
What is a Triangle?
A triangle is a polygon with three sides and three angles. The sum of the angles in any triangle is always 180 degrees.
Vertices: The points where two sides meet (A, B, C)
Sides: The line segments connecting the vertices (AB, BC, AC)
Angles: Formed at each vertex (∠A, ∠B, ∠C)
Types of Triangles by Sides
Equilateral Triangle
All sides are equal
All angles are 60°
Isosceles Triangle
Two sides are equal
Two angles are equal
Scalene Triangle
No sides are equal
No angles are equal
Types of Triangles by Angles
Acute Triangle
All angles are less than 90°
Right Triangle
One angle is 90°
Follows the Pythagorean theorem
Obtuse Triangle
One angle is greater than 90°
Triangle Formulas
Area of a Triangle
Base and Height
where b is the base and h is the height
Heron's Formula
where s = (a+b+c)/2 and a, b, c are the sides
Perimeter of a Triangle
where a, b, and c are the lengths of the sides
Pythagorean Theorem (Right Triangles)
where c is the hypotenuse (longest side) and a and b are the other two sides
Related Topics
Practice Triangles
Test your knowledge with our interactive triangle practice exercises.
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