$12.$ The triangular numbers are as follows:

$1=1$

$3=1+2$

$6=1+2+3$

$10=1+2+3+4$

$15=1+2+3+4+5$

$21=1+2+3+4+5+6$

etc.

The series begins with $1($the first triangular number$).$ To calculate the nth triangular

number, n is added to the previous triangular number. For example, the fourth triangular

number is calculated by adding $4$ to the third triangular number $($which is $6),$ i$.$e$.10=(1$

$+2+3)+4.$

Write a recursive function $($pseudocode$)$ in that will calculate the nth triangular number.

Note: will not receive any credit for a non$-$recursive solution.

For example, the following statements would lead to the underlined output:

Example $1$:

print $($ triNum$(1))$;

$1$

Example $2$:

print $($ triNum$(2))$;

$3$

Example $3$:

print $($ triNum$(5))$;

$15$

Note: you may assume the parameter will be positive $$ no error checking of inputs is

required