Triangular Number Python

PROGRAM TO CHECK IF A NUMBER IS TRIANGULAR

import math

  

# Returns True if num is triangular

def isTriangular(num):

  

    if (num < 0):

        return False

  

    # Considering the equation n*(n+1)/2 = num

    # The equation is : a(n^2) + bn + c = 0

    c = (-2 * num)

    b, a = 1, 1

    d = (b * b) - (4 * a * c)

  

    if (d < 0):

        return False

  

    # Find roots of equation

    root1 = ( -b + math.sqrt(d)) / (2 * a)

    root2 = ( -b - math.sqrt(d)) / (2 * a)

  

    # checking if root1 is natural

    if (root1 > 0 and math.floor(root1) == root1):

        return True

  

    # checking if root2 is natural

    if (root2 > 0 and math.floor(root2) == root2):

        return True

  

    return False

  

  

# Driver code

n = 55

if (isTriangular(n)):

    print("The number is a triangular number")

else:

    print("The number is NOT a triangular number")







OUTPUT

 The number is a triangular number 

CREDITS: https://www.geeksforgeeks.org/triangular-numbers/