if the mth term of an ap is 1/n and nth term is 1/m, show that the sum of the mn terms is mn+1/2

Note:

Dear Student, next time please put proper brackets while writing your question. Sometimes it becomes difficult for us to understand. 

In the above problem, you wrote prove that the sum is mn+1/2, which means, (mn+1)/2.

The way you have written could also mean mn + 1/2(that is, mn+half). Just a suggestion so that we can help you as much as possible without any hindrance. Thank you.