## 4680 Reputation

8 years, 131 days

## MaplePrimes Activity

### These are answers submitted by nm

in numerical integration, you can't have parameter with no numerical value in the integrand. (how is Maple going to find numerical value if a has no value?)

Assign a some value before calling int, then it will work

```a:=.4;
f := (x, y) ->(1/2)*a*(sinh(y-x^2)+tanh(x-y^3));
sol := evalf(int(int(f(x, y), x = -6 .. 5), y = -5 .. 5));```

or

```restart;

Explore(
evalf(int(int((1/2)*a*(sinh(y-x^2)+tanh(x-y^3)), x = -6 .. 5), y = -5 .. 5)),
a=1..10,initialvalues=[a=1],size=[800,60]
);
``` You can also use Explore, and change the raduis using the slider with the mouse.

```restart;
Explore(plots:-display( plottools:-sphere([0,0,0],r),view=[-3 .. 3,-3..3,-3..3]),
r=0.1..3.0,initialvalues=[r=0.5]):
``` always use exact numbers, unless there is a reason not to

```a := 12/100;
kn := n -> (n + 1/2)*Pi/a;
g := (n, x) -> cos(kn(n)*x);
g(1, a);```

0

You could try collect

```p:= (1+x+y)*(2*x-y*x+z)*(y^2-z*y);
collect(expand(p),x);
collect(expand(p),y);
collect(expand(p),z);
``` Just tell it the full specs of y(x) which is option after the ode and bc. This is needed when you have y(L) and y(x) in the input, so it knows which is the actual dependent variable to solve for.

And I is complex number by default So changed it to I__0 for the  second moment of area. You can use different symbol if you want.

```restart;
ode := diff(y(x), x\$2) = -P*x/(I__0*E);
bc  := y(L)=0,D(y)(L)=0;
sol := dsolve([ode,bc],y(x))
``` `odetest(sol,[ode,bc])`

[0, 0, 0]