Problem 860 (difficulty: 5/10)

\(\displaystyle \int |x|\dx=? \qquad\qquad \int |x^2-1|\dx=? \qquad\qquad \int {\sqrt{1+x^2}+\sqrt{1-x^2}\over \sqrt{1-x^4}}\dx=? \)

Give me another random problem!