exercise with arctg and (probably) differntial

Kangurur

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Nov 18, 2020
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[MATH]xarctgx>(1/2) (pi)-1[/MATH]

[MATH]x>=0[/MATH]I have no idea how to solve this. Help me please?
 
This does NOT involve a differential and certainly is NOT a differential equation! There is no "formula" or "trick" to this, just look for values of x so that \(\displaystyle x arctan(x)= 0\). It is simply algebra- solve this equation.

I would start by using "Desmos", https://www.desmos.com/calculator, to graph \(\displaystyle y= x arctan(x)\) and \(\displaystyle y= \frac{\pi}{2}- 1\). It appears that \(\displaystyle x arctan(x)>\frac{\pi}{2}\) for x< -0.826 and x> 0.826, approximately.
 
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