1. ## function problem

I am trying to compile this in DevC++ but I keep getting hung up with the error..
" 'h' cannot be used as a function." Is there something I`m missing? I`ve been assigning different letters to equations all night and this is the first problem I`ve had. Thanks for the help. Plain

Code:
```//Here's a piece on horizontal cylinders, circular and elliptical,
//that may be
//what you want.
//Consider a circle of radius a (the end of the tank)
//and imagine that the liquid
//has reached
//height h, measured from the lowest point on the circle.
//Note that  0 <= h <= 2a.  The area A
//of the segment of the circle covered by the liquid is
//A = pi*a^2/2 - a^2*arcsin(1-h/a) - (a-h)*sqrt(h(2a-h)).
//Now multiply A * L.
//This program calculates the partial volume of a horizontal cylinder.
//a = r, h = measured liquid
//

#include <cstdlib>
#include <iostream>
#include <math.h>
using namespace std;

int main()
{
double fillvol;
double pi = 3.141592;
double r;
double h;
double L;

cout << "Enter the radius of the circular cylinder in ";
cout << "decimal feet: ";
cin >> r;
cout << "The circular area of the cylinder is: ";
cout << ((r * r) * pi) << "feet.\n";

cout << "Enter the height of the liquid in decimal feet: ";
cin >> h;
cout << "The liquid height is " << h << "feet.";

cout << "Now enter the length of the cylinder: ";
cin >> L;

cout << "The volume of liquid in the cylinder is: ";
cout << L * ((pi * ((r*r)/2)) - ((r*r)*(asin(1-(h/r))) - (r-h)*sqrt(h(2r-h))));
cout << "cubic feet";

system("PAUSE");
return 0;
}```

2. Code:
`sqrt(h(2r-h))`
->
Code:
`sqrt(h * (2r-h))`
You can't just stick two numbers/variables together in C++ and hope they get multiplied together; you need to use the multiplication operator *.

3. If I recall, there is a define for pi in math.h and cmath (which you should use instead o f math.h). It's "PI".

4. Originally Posted by Desolation
If I recall, there is a define for pi in math.h and cmath (which you should use instead o f math.h). It's "PI".
Or not.

5. Of course! Thank you DWKS I should have known better.

The pi thing.....I`m lost can you enlighten me?

6. it's M_PI

7. Originally Posted by jarro_2783
it's M_PI
Or, as Homer would say, "Mmmmmmmmmmm, pi".

8. Originally Posted by jarro_2783
it's M_PI
Or not.

There isn't a standard symbol for pi.

9. Many compilers have M_PI, but some do not. It's best to define it yourself as you have done.

You got the value wrong, however.
Code:
`double pi = 3.141592;`
pi is 3.14159265358979... so it isn't 3.141592, it's 3.141593.