Sunday, April 28, 2019

calculus - Does a bijective map from $(−π,π)→mathbb R$ exist?



I'm having trouble proving that $\mathbb R$ is equinumerous to $(-π,π)$. I'm think about using a trigonometric function such as $\cos$ or $\sin$, but there are between the interval of $(0,1)$. Could someone help me define a bijective map from $(−π,π)→\mathbb R$?


Answer



You could use a trigonometric function such as $\tan$, although you must first divide the number by $2$ to instead get $\tan$ applied to a number in the interval $(-\pi/2,\pi/2)$.


No comments:

Post a Comment

analysis - Injection, making bijection

I have injection $f \colon A \rightarrow B$ and I want to get bijection. Can I just resting codomain to $f(A)$? I know that every function i...