Feed in the horizontal length of your zip line, and the difference in height between the two ends.
Also enter the difference in height between the high station and the lowest point of the line in use (you don't want the rider hitting the ground, or left dangling too high in the air!)
This app will show you where the rider's end point will be and required cable length.
|vertical dist AB
|vertical dist AC
|Horizontal dist AC
|Horizontal Dist AB