Problem: For every positive integer n, prove that 1+2+...+n=n(n+1)/2.
One can use Principle of Mathematical Induction.
for n=1, it is easy to check that both sides of the equation give the same value.
and RHS: 1(1+1)/2=1
Hence the statement is true for n=1.
Let the statement is true for some ...
A proof is provided. The solution is detailed and well presented.