∫√(9-x^2)dx=x√(9-x^2)-∫xd(√9-x^2)=x√(9-x^2)+∫x^2/√(9-x^2)dx=x√(9-x^2)+∫(9-(9-x^2))/√(9-x^2)dx=x√(9-x^2)+∫9/√(9-x^2)dx-∫√(9-x^2)dx从而2∫√(9-x^2)dx=x√(9-x^2)+∫9/√(9-x^2)dx所以∫√(9...