Perimeter of an isosceles triangle

Do you need to calculate the perimeter of an isosceles triangle? You can use our calculator that will allow you to know the length of an isosceles triangle by simply entering the measure of its sides.

And if you want to know more about this triangle with two equal sides, read on.

How to calculate the perimeter of an isosceles triangle

Isosceles triangle

As we have already mentioned, this type of triangles are characterized for having two equal sides and a completely different one. In the case of the triangle represented in the figure, you can see that the two equal sides are labeled with the letter 'a' while the different side corresponds to the letter 'b'.

With this in mind, we can calculate the perimeter of an isosceles triangle by applying the following formula:

Perimeter = a + a + a + b = 2a + b

Let's imagine that we have a isosceles triangle with side a = 8 centimeters and b = 4 centimeters. To calculate its perimeter we apply the previous formula:

P = a + a + a + b = 2a + b = 8 + 8 + 4 = 20 centimeters.

Area of an isosceles triangle

To calculate the area of a triangle isosceles there are several methods. All of them you will find in the link that we have just left and from which we will tell you how to get the surface of any triangle, regardless of whether it is isosceles or otherwise.


Characteristics of the isosceles triangle

Perimeter of a triangle

Although we have already mentioned it at the beginning, the isosceles triangle has the following characteristics characteristics:

  • Two of its sides are equal
  • The angles opposite to those sides of equal length are also similar.
  • The angle Beta can be calculated by applying the following formula: Beta = 180 - 2 x alpha

Height of the isosceles triangle

Formula for calculating the height of an isosceles triangle
Formula for calculating the height of an isosceles triangle

For Calculate the height (h) of an isosceles triangle.we have to recourse to the Pythagorean Theorem once again. In this case, we should know that:

  • The hypotenuse will be the length of side a
  • The shortest leg will measure b/2
  • The longest leg will give us the value of the height we are looking for.

To make this calculation, you can use our online calculator, which you will find in the link at the beginning of this section, or if you prefer, you can also use the manual calculation from the formula you have above these lines.

Types of isosceles triangles

Types of isosceles triangles

We have already seen that an isosceles triangle has two equal sides and two similar angles. Depending on how that remaining angle is, isosceles triangles can be classified as:

  • Acutangle: all sides have less than 90 degrees
  • Rectangle: the unequal side is 90º.
  • Obtuse angle: the unequal side has more than 90º but less than 180º.

In the image above you can see an image of each type so that it is clear how they are classified.

2 thoughts on “Perímetro de un triángulo isósceles”

    • You would have to pose a system of equations and apply the Pythagorean Theorem:

      2a + b = perimeter
      b/22 + height2 = a2

      You solve it, you got it.

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