Copied Evaluate by contour integration \[ I=\int _0^\infty \frac {x\sin 3x}{4+x^2}\,dx. \] Raw LaTeX Evaluate by contour integration \[ I=\int_0^\infty \frac{x\sin 3x}{4+x^2}\,dx. \] Topic Tags Contour Integration and Residue Calculus Keyhole and Sector Contours Linear Programming and Optimization Real Integral Evaluation by Complex Methods