# Building a Double Integral Calculator

Marcos Paulo shared this problem 3 years ago
New

Hey there guys,

I saw a lot of materials on calculating Double Integrals here on the site, but none of them made everything I wanted clearly, so I decided to make my own. In that sense, I want to see three things when I'm calculating a Double Integral:

(i) Step-by-step algebraic process, until the final numeric result: Most of the time I make 1 or 2 little mistakes when calculating Double Integrals, but those lead to very different results, so I want to check every step of my calculus.

(ii) Domain Sketching: Sometimes I don't even know how the domain is going to look like, so I end up putting wrong boundaries on the integral. I'm pretty sure GeoGebra can sketch any domain better than I do haha.

(iii) 3D Representation: Even when I do get right results, most of the time I don't know VISUALLY what I'm calculating. The goal here is to show the volume of the "thing" which I'm calculating.

I came across some problems though, and I've tried looking for solutions here on the forum, but since I'm not a advanced user, I didn't find any. Here are them:

1) The integral constants keep showing up: I want this calculator ready to be used right when someone open it up, but every time I do open it, the algebraic result is filled with integral constants. I wouldn't consider those when I'm calculating a volume.

2) I don't know how to code (iii): What I want is that the functions I type in on the algebraic calculator ( f(x) & g(x) ) show up as shapes in the "Volume Representation" screen, so they can be limited inferiorly by the x-y plane and superiorly by f(x,y), forming a "thing" which the Double Integral is calculating the volume.

I'll post the .ggb file and some screenshots of the calculator here so you guys can understand what I'm asking. 2

if(y>=g(x)&&y<=f(x),f(x,y)) change name of f(x,y) 1

Didn't get it; why should I change the name of my f(x,y)? 