Find ∫cosxx2+1dx\int \frac{\cos x}{x^2+1} dx∫x2+1cosxdx is not elementary. What is the value of ∫0∞cos(ax)x2+1dx\int_0^\infty \frac{\cos(ax)}{x^2+1} dx∫0∞x2+1cos(ax)dx?
π2e−a\frac{\pi}{2} e^{-a}2πe−a
π2ea\frac{\pi}{2} e^{a}2πea
πe−a\pi e^{-a}πe−a
e−ae^{-a}e−a