80. Problema: Calcule \int \frac{x^2 + 1}{x^4 + 1} \, dx.
\arctan x - \frac{1}{2} \ln |x^2 - \sqrt{2} x + 1| + C
\frac{1}{x^2 + 1} + C
\frac{x}{x^2 + 1} + C