recursion describe related approach to proving theorems using inductionwe could define the triangular numbers mathematically by saying tri( if tri(nn tri( - if defining something in terms of itself may seem circularbut in fact it' perfectly valid (provided there' base casefactorials factorials are similar in concept to triangular numbersexcept that multiplication is used instead of addition the triangular number corresponding to is found by adding to the triangular number of - while the factorial of is found by multiplying by the factorial of - that isthe fifth triangular number is + + + + while the factorial of is * * * * which equals table shows the factorials of the first numbers table factorials number calculation factorial by definition * * * * , , , , , the factorial of is defined to be factorial numbers grow large very rapidlyas you can see recursive method similar to triangle(can be used to calculate factorials it looks like thisint factorial(int nif( == return else return ( factorial( - )