12.1    a) integral x^3/3 dx
        b) integral 4/sqrt(x) dx
        c) integral 5*x*sqrt(x) dx
        d) integral sqrt(x)*(x^2-5x) dx
        e) integral (2x^(-2/3)+3^(-2)) dx
        f) integral (x^2/2-2/(x^2)) dx
        g) integral (1/x^2-1/(2sqrt(x)))^2 dx
        h) integral (3x^2-4x+5sqrt(x))/(x^2) dx
        i) integral (x^2-2x+x^(1/5))/(x^(1/3)) dx
        j) integral 2^x*5^x+e dx
        k) integral (e^x+ln(2))^2 dx
        l) integral 1/e^x dx
        m) integral 2^x/4^x dx
        n) integral x^2/(x^2+1) dx
        o) integral x^4/(x^2+1) dx
        p) integral sqrt(1+(x^2+x^4)/(1-x^4)) dx
        q) integral (1+sqrt(2))/(sqrt(2-2x^2)) dx

12.2    a) integral cos(x+2) dx
        b) integral sin(3x) dx
        c) integral (3x-2)^7 dx
        d) integral (7-2x)^(1/3) dx
        e) integral e^(-2x+8) dx
        f) integral 1/(3x+5) dx
        g) integral 1/(x^2+4) dx

12.3    a) integral x/sqrt(x^2+5) dx
        b) integral 3^(sqrt(x))/sqrt(x) dx
        c) integral x^2*e^(x^3) dx
        d) integral (2x+7)/sqrt(1-x^2) dx

12.4    a) integral 1/(x*ln(x)) dx
        b) integral ln(x^3)/(2x) dx
        c) integral 1/(x*ln(x)*ln(ln(x))) dx
        d) integral arctan(x)*(1+x^2) dx
        e) integral 2x/(x^4+3) dx
        f) integral x^2/(x^2+5) dx
        g) integral 1/sqrt(4-x^2) dx
        h) integral 1/(x^2+2x+2) dx

12.5    a) integral x*sqrt(1-x) dx
        b) integral x^3*sqrt(1-x^2) dx

12.6    a) integral 1/(1+sqrt(x)) dx
        b) integral 1/(sqrt(e^x-1)) dx
        c) integral e^(2x)/(1+e^x)^(1/4) dx