Function fxydxdy

fxydxdy(
    func: ChalkboardFunction,
    xinf: number,
    xsup: number,
    yinf: number,
    ysup: number,
): number
Calculates the double integration of a multivariable function.
Parameters
- func: ChalkboardFunction
  The function
- xinf: number
  The lower x-bound
- xsup: number
  The upper x-bound
- yinf: number
  The lower y-bound
- ysup: number
  The upper y-bound
Returns number
Example
```
const f = Chalkboard.real.define((x, y) => x + y);
const integral = Chalkboard.calc.fxydxdy(f, 0, 1, 0, 1); // Returns approximately 1
```
- Defined in Chalkboard.calc.ts:660