Something cool that I have not yet seen ! :)
Circle "tangent" can be draw along the "helpers lines"

Take the Circle "tangent" function
Draw somes "helpers lines"
Clic 2 points on these helpers lines
The possible circles are drawing moving !

Ps Request : "Helpers lines" can be also " Helpers circles"
Seems that will be great :)
Rules and dividers are the bases of geometry :)