1sttriangularnumber

<-- Enter triangular number statement
  

Calculate triangular number 1

The formula for triangular number n is as follows
Tn  =  n(n + 1)
  2

Given n = 1, we have:
T1  =  1(1 + 1)
  2

T1  =  1(2)
  2

T1  =  2
  2

T1 = 1