# A sum with irrational limits

#### romsek

Math Team
That result isn't correct. For n=5 the sum equals approximately 0.81, and your right hand side equals approximately 0.293

You could have checked that yourself.

#### Integrator

That result isn't correct. For n=5 the sum equals approximately 0.81, and your right hand side equals approximately 0.293

You could have checked that yourself.
Hello,

Attention!If the limits of the sum are irrationals and $$\displaystyle \sqrt{2} \leq k \leq \sqrt{5}$$ , then how does the value of $$\displaystyle k$$ vary?
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Four questions:
1) How many terms does he have $$\displaystyle \sum_{k=\sqrt{2}}^{\sqrt{2}} \frac{1}{k(k+1)}$$?
2) How many terms does he have $$\displaystyle \sum_{k=\sqrt{2}}^{\sqrt{3}} \frac{1}{k(k+1)}$$?
3) How many terms does he have $$\displaystyle \sum_{k=\sqrt{2}}^{\sqrt{4}} \frac{1}{k(k+1)}$$?
4) How many terms does he have $$\displaystyle \sum_{k=\sqrt{2}}^{\sqrt{5}} \frac{1}{k(k+1)}$$?
Thank you very much!

All the best,

Integrator

Last edited:

#### romsek

Math Team
I'm done. If you want to write up how to do sums with irrational indices that don't obey the common sense translation you said yes to in post #3 then have at it.

• topsquark

#### Integrator

I'm done. If you want to write up how to do sums with irrational indices that don't obey the common sense translation you said yes to in post #3 then have at it.
Hello, I was wrong!Thousands of apologies! I was thinking about the limits of the sum .... If I didn't upset you too much, then I would like we continue the discussion.Thank you very much!

All the best,

Integrator