13.1   a) integrate [x*e^x] dx
       b) integrate [x*cos x] dx
       c) integrate [x*sin(2x+1)] dx
       d) integrate [x*3^(-x)] dx
       f) integrate [arcsin x] dx
       g) integrate [ln x] dx
       h) integrate [ln(x^2+1)] dx

13.2   a) integrate [x^2*sin x] dx
       b) integrate [x^3*e^x] dx
       d) integrate [e^x*sin(x)] dx
       f) integrate [sin(ln(x))] dx

13.5   c) integrate [1/(x^2-4)] dx
       d) integrate [(x-8)/(x^3-4x^2+4x)] dx
       g) integrate [(y-9)/(2y^2-3y+1)] dy
       j) integrate [((x-2)(x+2))/(x^3*(x-1))] dx
       k) integrate [(x+4)/(x(x^2+2x+2))] dx
       l) integrate [(16x+32)/(x^4-16)] dx

13.7   b) integrate [(x^3+1)/(x^3-x^2)] dx
       d) integrate [(x^3+4x^2)/(x^2+3x+2)] dx

13.8   a) integrate [(sin(2x))/(3-sin(x))^3] dx
       b) integrate [(2x^3+3x-5)/(x^2+x-2)^2] dx
       c) integrate [(2x^3+x^2+8x+10)/((x^2+1)(x^2+6x+10))] dx