How to calculate area of triangle given the length of sides?

To apply any formula to calculate area of a triangle, one must know the value of at least one angle of the triangle. However, there is one formula for calculating the area of a triangle without measuring any of its angles.

In this article, we will use Heron’s formula, named after the Hero of Alexandria, a Greek mathematician. It takes three lengths (a,b, c) of a triangle and semi-perimeter s. In order to apply this formula, it is mandatory to know the lengths of all three sides of the triangle.


A = √s (s - a) (s - b) (s - c)

where, a, b and c are the lengths of sides of the triangle where s is half of the perimeter given by s=(a+b+c)/2.

Mathematical illustration

calculate area of triangle using python
Heron’s Formula to calculate area of triangle


While coding, using Heron’s formula is not going to be a challenging task for you if you can compute the square root using a custom or built-in function. Now, let’s have a python program to evaluate the area of a triangle by using the length of the sides.

def calculateArea(a, b, c):
  	 s= (a+b+c)/2  #s is the semi perimeter
  	 area= math.sqrt(s*(s-a)*(s-b)*(s-c))
  	 return area
print(calculateArea (4, 6, 8))
  • Line 1: Function definition to calculate the area of a triangle using given sides i.e. a, b, and c.
  • Line 2: Calculating the semi perimeter of the triangle by calculating the sum of sides & dividing it by 2.
  • Line 3: Computing the area by calculating the square root of the product of s(s-a)(s-b)(s-c).
  • Line 4: Returning the area computed by calculateArea().
  • Line 6: Invoking calculateArea() method with 4, 6, and 8 values for a, b, and c respectively to calculate the area of a triangle. 


calculate area of triangle using python

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