Answer
$y=\pm x$ or $y=|x|$
Work Step by Step
Step 1. Given the function $y=\sqrt {x^2+1}$, we need to find all the oblique asymptotes.
Step 2. We need to find the end behavior or the limits of the function when $x\to\pm\infty$.
Step 3. $\lim_{x\to\infty}y=\lim_{x\to\infty}\sqrt {x^2+1}=\lim_{x\to\infty}x\sqrt {1+\frac{1}{x^2}}=x$
Step 4. $\lim_{x\to-\infty}y=\lim_{x\to-\infty}\sqrt {x^2+1}=\lim_{x\to-\infty}(-x\sqrt {1+\frac{1}{x^2}})=-x$
Step 5. Thus, the oblique asymptotes are $y=\pm x$ or $y=|x|$
