Could there be an irrational number $x$ such that the product of $x$ and $\pi$ are rational?

200 Views Asked by At

I know that irrational numbers cannot be the quotients of any two rational numbers, and an irrational number times a rational number is thus also irrational. But, could there be an irrational number, that, when multiplied by $\pi$, the product is rational?

1

There are 1 best solutions below

0
On

If $r=x\pi$ where $r$ is rational, then we have $x=\frac r\pi$.

This means that if you have an $x$ such that $x\pi$ is rational, then $x$ is of the form $\frac k\pi$ for some rational $k$. This explains why the answer to your question should always be "derived from $\pi$".