Desmos domain error?

$\begingroup$

Just curious if anyone has an idea why Desmos would claim that $f(0)=0$ for $f(x)=\frac{1}{\frac{1}{x}}?

As a note of interest, Geogebra commits the same error but both Symbolab and Wolfram get it right.

Any thoughts?

$\endgroup$ 4

2 Answers

$\begingroup$

Desmos simplifies functions before evaluating them, to save time. Since desmos is a graphing calculator, the small bit of time saved is not insignificant when dealing with the thousands of points required to represent a curve. While Desmos does check for domain errors in basic cases, many times it does not, and you are observing one of them. Desmos evaluates $\frac{1}{NaN}$ to be 0, so for example, try $\frac{1}{\tan(\frac{\pi}{2})}$ and you will get zero as well. Desmos does not however, simplify $\frac{NaN}{NaN}$ or $\frac{0}{0}$ so $\frac{x}{x}$ is undefined at $x=0$

$\endgroup$ 5 $\begingroup$

They work on the Extended Number Line so 1/0 is ∞ then 1/∞ = 0 again

Note that 0/0 = undefined (NaN) is handled differently

$\endgroup$

Your Answer

Sign up or log in

Sign up using Google Sign up using Facebook Sign up using Email and Password Submit

Post as a guest

Post Your Answer Discard

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy