9.1     a) differentiate 6x-1
        b) differentiate 2x^2-5x
        c) differentiate x^3
        d) differentiate sqrt(3x)
        e) differentiate 1/x

9.2     a) differentiate pi^2x^5
        b) differentiate x-6sqrt(x^3)
        c) differentiate 3/e^3+2/sqrt(x)
        d) differentiate sqrt(pi)-ln(x*e^x)
        e) differentiate (x^2*arctan x + sqrt(x) + 1)/(x^2)
        f) differentiate sin^2 x + cos^2 x

9.3     a) differentiate x^5 * arcsin x
        b) differentiate 3cos x /(5x)
        c) differentiate (x+x^2)/(ln x)
        d) differentiate (x*e^x)/(sin x)

9.4     a) differentiate (4x-3)^5
        b) differentiate 1/cos(x)
        c) differentiate sin^2(3x)
        d) differentiate sqrt(ln(sin(x^3)))
        e) differentiate tan^2(10^(arctan(sqrt(x))))
        f) differentiate (arccos((ln(cos^2(5x)))^(1/3)))^3
        g) differentiate ((2x+1)/(3x-2))^2
        h) differentiate ln((4x-3)^3/(x))
        i) differentiate arctan((1-x)/(1+x))
        j) differentiate x^(sin(x))
        k) differentiate (ln(x))^x

9.5     a) second derivative ln x
        b) 13th derivative sin x
        c) 10th derivative 2x^5+6x^2

9.6     a) third derivative cos^2 x at x = pi/4
        b) fourth derivative x*e^x at x = 2