Python Program to find Area Of a Triangle

How to write Python Program to find Area Of a Triangle, Perimeter of a Triangle and Semi Perimeter of a Triangle with example. Before we step into the Python Program to find Area Of a Triangle, Let see the definitions and formulas behind Perimeter and Area Of a Triangle.

Area Of a Triangle

If we know the length of three sides of a triangle then we can calculate the area of a triangle using Heron’s Formula

Area of a Triangle = √(s*(s-a)*(s-b)*(s-c))

Where s = (a + b + c )/ 2 (Here s = semi perimeter and a, b, c are the three sides of a triangle)

Perimeter of a Triangle = a + b + c

Python Program to find Area of a Triangle & Perimeter of a Triangle

This Python program allows the user to enter three sides of the triangle. Using those values we will calculate the Perimeter of a triangle, Semi Perimeter of a triangle and then Area of a Triangle.

a = float(input('Please Enter the First side of a Triangle: '))
b = float(input('Please Enter the Second side of a Triangle: '))
c = float(input('Please Enter the Third side of a Triangle: '))

# calculate the Perimeter
Perimeter = a + b + c

# calculate the semi-perimeter
s = (a + b + c) / 2

# calculate the area
Area = (s*(s-a)*(s-b)*(s-c)) ** 0.5

print("\n The Perimeter of Traiangle = %.2f" %Perimeter);
print(" The Semi Perimeter of Traiangle = %.2f" %s);
print(" The Area of a Triangle is %0.2f" %Area)

The first three Python statements will allow the User to enter the three sides of the triangle a, b, c. Next, Calculating the Perimeter of Triangle using the formula P = a+b+c.

# calculate the Perimeter
Perimeter = a + b + c

Next, Calculating the semi perimeter using the formula (a+b+c)/2. Although we can write semi perimeter = (Perimeter/2) but we want show the formula behind. That is why we used standard formula

s = (a + b + c) / 2

Calculating the Area of a triangle using Heron’s Formula:

(s*(s-a)*(s-b)*(s-c)) ** 0.5

Python Program to find Area of a Triangle using functions

This python program allows the user to enter three sides of the triangle. We will pass those three values to the function arguments to calculate the area of a triangle in Python.

# Area of a Triangle using Functions

import math

def Area_of_Triangle(a, b, c):
    
    # calculate the Perimeter
    Perimeter = a + b + c
    # calculate the semi-perimeter
    s = (a + b + c) / 2

    # calculate the area
    Area = math.sqrt((s*(s-a)*(s-b)*(s-c)))

    print("\n The Perimeter of Traiangle = %.2f" %Perimeter);
    print(" The Semi Perimeter of Traiangle = %.2f" %s);
    print(" The Area of a Triangle is %0.2f" %Area)

Area_of_Triangle(6, 7, 8)

Python triangle area output

 The Perimeter of Traiangle = 21.00
 The Semi Perimeter of Traiangle = 10.50
 The Area of a Triangle is 20.33
>>> Area_of_Triangle(10, 9, 12)

 The Perimeter of Traiangle = 31.00
 The Semi Perimeter of Traiangle = 15.50
 The Area of a Triangle is 44.04
>>> 

First, We imported the math library using the following statement. This will allow us to use the mathematical functions like math.sqrt function

import math

Step 2: Next, We defined the function with three arguments using def keyword. It means, User will enter the three sides of the triangle a, b, c.

Step 3: Calculating the Area of a triangle using Heron’s Formula: sqrt(s*(s-a)*(s-b)*(s-c)); (sqrt() is the mathematical function inside the math library, which is used to calculate the square root.

NOTE: Please be careful while placing the open and close brackets, it may change the entire calculation if you place it wrong