Original subtitles

What is going on, guys, and welcome to our first example that we are doing and these recursions section

of this video, in this example, we are going to write a function, a recursive function that will

receive some naturale number, which is numb, and then it will return the sum of the arithmetical progression

from one up to number.

So we are going to write a recursive function that will call itself and once it calls itself, it will

divide.

The main problem into some sub smaller sub problems until it reaches some stopping condition.

And the result will be to find the sum from one up to number.

So, for example, if we received anomic Wil's two three, then our recursive function should return

the sum of one plus two plus three, which is a total of six.

And if we received Nomic was two five, then our recursive function should return the sum of one plus

still plus three plus four plus five, which is a total of fifteen.

So as we can see, the sum of all the numbers from one up to number five for all their natural numbers

from one to NUM.

So that's what we want to do in this exercise, in this example.

And we know that it can be done easily just by using some for a loop or while loop.

Right.

But we are going to use our new concept, our recursion concept, to solve this exercise and to make

things a little bit easier for us.

I suggest to write or some is the following way.

One plus two plus three on so on up until you sum num minus one and the num itself to your general sum.

Okay.

And instead of looking at these sum in this way, it's just a hint that you may also look at the sum

in the following way, which is pretty much the same.

Right.

It doesn't matter if you some from left to right or from right to left.

The sum is going to be the same.

But that's the first hint that I give you to solve this example and take a few moments to think about

how you would do it.

And we are going to solve it together.

So let's go.