I broke Maple!!!

Factual Questions
1

I’m a complete Maple noob, but I didn’t think that I was this noobish.
Alls that I want to do is integrate a function from -10 to some number t, and then solve it for t.

Well, fine, might as well tell you the whole story since I’ve gone this far. Guy has a cylindrical gas tank, which is 10 feet in radius, and length doesn’t matter. This tank is on its side. If you were to stick a stick straight down the top of it, and the tank’s full, you’ll see 20 feet of wet stick when you pull it out. If it’s half full, you’ll see 10 feet of wet stick. My task is to figure out how much of the stick is wet when the tank is 1/4 and 3/4 full.

So I look at the cross-sectional area, and look only at the top half of the circle, so I can express my equation in terms of y (y=sqrt(100-x^2)), multiplied by 2 because I am looking at a semicircle. I am assuming that this is correct, but I can’t get maple to do my definite integral.

So, I can do this

int(sqrt(100-x^2),x); and it works fine.

It goes insane when I tell it to do a definite integral, like
int(sqrt(100-x^2),x,x=1…2);
it goes nuts and tells me
Error, (in int/check_syntax) Illegal argument x = 1 … 2

See, what I really want to do is something like
solve(12.5*Pi=int(sqrt(100-x^2),x,x=-10…t),t);

Any suggestions?

2

Try taking out that second argument of ,x, - you want it for the indefinite integral, but not the definite.

int(sqrt(100-x^2),x=1…2);

and

int(sqrt(100-x^2),x=1…t);

work nicely (at least in v9.5 – what version are you in? I’ve just moved to 10, and I’m not liking it one bit …)

3

I’m using… Maple 6. :confused:

It’s not solving “> solve(12.5*Pi=int(sqrt(100-x^2),x=-10…t),t);” for whatever reason.

4

v6 … ouch. The oldest one I’ve got is v7, and I’d need to reinstall it.

I suppose there’s not much comfort in knowing that that syntax is exactly correct in later versions (I copied, pasted, and solved to -4.039727533).

Couple possible things to explore - can you tell if it’s having trouble on the integration step, or the solve step? What does

f:= int(sqrt(100-x^2),x=-10…t);

solve(12.5*Pi = f,t);

get you?

5

Nothing. It just goes to the next line and doesn’t output ANYTHING, just like when I tried the syntax I described above. The school computer labs have Maple 9 on them, and I’ll be able to use them tomorrow. My “after-hours” access to the lab closes at 10pm, and I missed my window tonight (barely). I can do that tomorrow morning, I just want to get it done tonight because what if I can’t get it done in the hour or so I’ll have tomorrow morning? :eek:

6

Not even an error message? Wow. I’m sorry, I don’t know what to tell you :frowning: And yes, it even checks out in 7. If it was giving you an expression for the integral, my next suggestion would have been to try fsolve instead of solve (since I’m getting a floating point solution, not exact). Without the expression … hmmm, you said it would give you an expression for the indefinite integral

int(sqrt(100-x^2),x);

OK? How determined are you to get it done tonight? I can think of one sort of ugly workaround that might do it … or not.

7

Works flawlessly in the school computer lab with maple 9 (and maple 10? That’s new on here.)

Sorry about eating up your time last night. :confused: