# Doubt from trignometry

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It resembles Fejer's inequality but cant find a Wiki link to it. Give me some time

Sir whenever free kindly share your approach

I am trying but not getting idea

@Hari_Shankar sir

Are you talking of this??

- Sir its concept out of my mind can you explain it little bit??

These all solution dont giving idea about upper bound why only it should be less then {2\sqrt{\pi}}

\displaystyle \sum_{k=1}^n \left(\frac{sin{kx}}{k}\right) is a Fourier series of a sawtooth wave

I tried to find a Fourier series of a sawtooth wave but that doesn't go good

All I get that the amplitude of sawtooth wave here is 1

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I found the function

\frac{π-x}{2}+π[\frac{x}{2π}]

For 0<x<π

[•] is GIF

I was talking about that pi -x/2 Part

Saw this on stackexchange

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Thanks for this one