7.4     a) plot -x^2+1
        b) plot log(-x), log(x)
        c) plot sin(x-pi)
	d) plot pi/2 + arcsin x, arcsin x where x=-3..3, y = -3..3
        e) plot e^(-2x) , e^(-x), e^x where x = -3..3
        f) plot cos(x)
        g) plot cos(2x), cos x 
        h) plot cos(3x), cos x
        i) plot sin(x/2), sin(x)
        j) plot sin(x/4), sin(x)
        k) plot tan(2x), tan x
        l) plot tan (x-2*pi), tan x

7.6     A) plot tan x
        B) plot 1/x
        C) plot arctan(x)
        D) plot sin(x)
        E) plot arcsin x
        F) plot cos(x)
        G) plot e^(-x)
        H) plot 1/sqrt(x), 1/x, 1/x^2 where x= 0..10
        I) plot e^x
        J) plot pi/2+arcsin(-x)
        K) plot x^4
        L) plot sqrt(x)
        M) plot ln(x)
        N) plot x^5, x^3
        O) plot 1/x^2

7.9     a) plot sqrt(x+4)
        b) plot sqrt(x^2-4)
        c) plot log(x-6) where x from 0 to 20
        d) plot y=sqrt(3), y= 1/log_10(3), y=1/log_10(1-x)+sqrt(x+2),  where x=-2..1, y=-10..10
        e) plot 1/ln(2-x)
        f) plot arcsin(2x-1)
        g) plot arccos(2/(1+x))
        plot 2/(1+x)
        plot arccos x

7.10    a) plot 3/x - x^3
        b) plot x(5^(2x)-5^(-2x))
        c) plot arcsin x/arctan x
        d) plot sin(x)-x*cos(x)
        e) plot sin x - cos x

7.11    a) plot sin(2x)
        b) plot cos(3x) 
        c) plot x^2
        d) plot tan(x/2)+3