# Using Google Dart as an online collaboration calculator

How to use Dart as an online collaboration tool

When I’m stuck on math questions I turn to my friend Chris who can write pixel perfect C# code in a chat window. Yesterday I needed to calculate where a line intersects a circle so after a few internet searches I came up with this Dart code:

```
double x1=100.0;
double y1=100.0;
double x2=200.0;
double y2=200.0;
double radians=Math.atan2(y2-y1, x2-x1) ;
double radius=50.0;
double y3=y2+radius * Math.cos(radians);
double x3=x2+radius * Math.sin(radians);
```

As it turned out, I made two mistakes. The last two lines should be:

```
double y3=y1+radius * Math.sin(radians);
double x3=x1+radius * Math.cos(radians);
```

How did I find out? Easy! I entered the code in the Dart editor and sent the generated link to Chris. He looked at the code, made some changes and sent a link back.

## Calculate intersection point of line and circle

I wrote this post to point out the power of a shared code editor and to show how to calculate where a line intersects a circle. Open the link in a recent Chrome or Firefox browser and press play!

Written by

**Loek van den Ouweland**on October 14, 2011. Questions regarding this artice? You can send them to the address below.