Here this example focuses on how to calculate the triangle area with Python.

### Method

Assuming the sides of the triangle are *a*, *b*, and *c* respectively, the area of the triangle can be obtained by the Helen formula:

S = sqrt[p(p-a)(p-b)(p-c)]

The *p* in the formula is a half cycle: * p = (a+b+c)/2*

### Source Code

```
#! /usr/bin/env python3
# -*- coding: utf-8 -*-
# Enter three sides
a = float(input('Enter the first side of the triangle: '))
b = float(input('Enter the second side of the triangle: '))
c = float(input('Enter the third side of the triangle: '))
# Calculated area based on Helen formula
temp = (a + b + c) / 2
area = (temp * (temp - a) * (temp - b) * (temp - c)) ** 0.5
# Print out area
print('The area of the triangle is %0.2f' % area)
```

Output:

1) Equilateral triangle

```
Enter the first side of the triangle: 5
Enter the second side of the triangle: 5
Enter the third side of the triangle: 5
The area of the triangle is 10.83
```

2) Right triangle

```
Enter the first side of the triangle: 3
Enter the second side of the triangle: 4
Enter the third side of the triangle: 5
The area of the triangle is 6.00
```

3) Isosceles triangle

```
Enter the first side of the triangle: 3
Enter the second side of the triangle: 3
Enter the third side of the triangle: 5
The area of the triangle is 4.15
```

### Think More

You can also add a judgment to determine whether the three sides can form a triangle.