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Triangle Perimeter Formula

There are 3 perimeter formulas for a triangle depending on whether it is scalene, equilateral or isosceles.

Scalene Triangle

When all 3 sides have different lengths, the perimeter is the sum of all three:

Scalene triangle perimeter formula: P = a + b + c
Pperimeter of the triangle a, b, ceach of the three sides with different lengths

Equilateral Triangle

When all 3 sides are equal, the perimeter is simply 3 times the length of one side:

Equilateral triangle perimeter formula: P = 3l
Pperimeter of the triangle llength of any side

Isosceles Triangle

When 2 sides are equal and the third is different:

Isosceles triangle perimeter formula: P = 2l + a
Pperimeter of the triangle llength of one of the equal sides athe side with a different length

More About the Triangle

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Fórmula del Área del Triángulo

Triangle Area
Formula

Triangle Perimeter
Formula

Interior and
Exterior Angles

Compass-and-Ruler
Construction

Right Triangle

Types by
Angles

Types by
Sides
Calculadora del Área del Triángulo

Triangle Area
Calculator
Calculadora del Perímetro del Triángulo

Triangle Perimeter
Calculator
El Triángulo en las Pirámides

Triangles in
the Pyramids

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