1340ForShowA27.mws

1340ForShowA27.mws
Thu Oct 27 13:08:55 MDT 2005

>    restart:

Page 98 of our Text -- Integration

Antiderivatives:   Int(cos(2*x),x)  via Maple

>    Int( cos(2*x) , x);

Int(cos(2*x),x)

>    value(%);

1/2*sin(2*x)

Maple doesn't do "+ C"

Nobody knows a nice Calculus-I antiderivative for exp(-x^2) :

>    Int(  exp(-x^2), x);   value(%);

Int(exp(-x^2),x)

1/2*Pi^(1/2)*erf(x)

Or for e^sec(x^2)  

>    Int(  exp(sec(x^2)), x);   value(%);

Int(exp(sec(x^2)),x)

int(exp(sec(x^2)),x)

Definite integrals Int(tan(x),x = 0 .. Pi/4) :

>    rex := Int( tan(x), x=0..Pi/4);

rex := Int(tan(x),x = 0 .. 1/4*Pi)

>    value(rex); evalf(%);

1/2*ln(2)

.3465735903

>    rex := Int( tan(x), x=0..Pi);  value(rex);

rex := Int(tan(x),x = 0 .. Pi)

undefined

>    rex := Int( tan(x), x=0..Pi/2);  value(rex);

rex := Int(tan(x),x = 0 .. 1/2*Pi)

infinity

The derivative of Int(tan(u),u = 0 .. x)  -- FTC-I in Chapter 5 of 170 text

>    F := unapply(   Int( u^3 - 2*u, u=0..x),  x);

F := proc (x) options operator, arrow; Int(u^3-2*u,u = 0 .. x) end proc

>    D(F);

proc (x) options operator, arrow; x^3-2*x end proc

Section 7.1:

We now calculate the area under the graph of f(x) = e^(-x^2)  from -1 to 2:

>    f := x -> exp(-x^2);

f := proc (x) options operator, arrow; exp(-x^2) end proc

>    XRG := -1..2:

>    Area := Int( f(x) , x=XRG);

Area := Int(exp(-x^2),x = -1 .. 2)

>    evalf( value(Area));

1.628905524

Maybe we should plot first to make sure we aren't missing something:

>    plot(f,XRG);

[Maple Plot]

Now go for the area:

>    value(Area);

1/2*erf(1)*Pi^(1/2)+1/2*erf(2)*Pi^(1/2)

Broaden the integration range:

>    Int(f(x), x=0..5280);  value(%);  evalf(%);

Int(exp(-x^2),x = 0 .. 5280)

1/2*erf(5280)*Pi^(1/2)

.8862269255

>    Int(f(x), x=0..infinity);  value(%);  evalf(%);

Int(exp(-x^2),x = 0 .. infinity)

1/2*Pi^(1/2)

.8862269255

Section 7.1 in the MATH-171 Text

Section 6.1 in the Calculus Text: the area between two curves.  6.1: 36

Find the area of the region boxed in by f and g, where f(x) = 2-x^2  and g(x) = exp(x)

>    f := x -> 2-x^2;

f := proc (x) options operator, arrow; 2-x^2 end proc

>    g := exp;

g := exp

>    XRG := -2..1:

>    plot([f,g], XRG, colour=[red, black], legend=["f","g"]);

[Maple Plot]

>    A := fsolve(f(x)=g(x), x=-2..-1);

A := -1.315973778

>    B := fsolve(f(x)=g(x), x=0..1);

B := .5372744492

>    Area := Int( f(x) - g(x), x=A..B);

Area := Int(2-x^2-exp(x),x = -1.315973778 .. .5372744492)

>    value(%);

1.452013983

>    ##########################################

>   

>