We know it's a curve to the right.  What we don't know (yet, the OP might still be able to provide it) is the bearing of line into the PC.  We know the Radius and the Central Angle (Delta).  That's all we need.  The bearing of the Chord is (in this case) equal to the bearing of the line to the PC - Delta/2.  Now it's simply a matter of drawing the lead line, a perpendicular line with the Radius to the centerpoint, and a circle.  The PT (point of tangency) will be the intersection of the circle and the chord line.

Dave.

Bonjour Phillipe,

Hello CarlB, thanks again for your explanations ( I know what is a chord, an arc, an arrow ).

uploads/353260/ArcLength.lsp Try out the attached ArcLength.lsp with its ARCL command [a new .LSP version I just made of what I've had as a screen menu item for many years] -- a way to draw an Arc including specifying the LENGTH ALONG THE CURVE [an aspect you can't use in AutoCAD's ways of drawing Arcs, unless that's been changed in a newer version than mine].  It was designed for property-description Arcs like your example.  It asks for the start point [defaulting to the last point, usually of a preceding Line but including getting it right for a preceding Arc if that was drawn with this command], starting direction [defaulting to tangent continuation as is so often the case in property boundaries], radius, length along the Arc, and whether it curves left or right. At this point that's the only variety of Arc it draws, but I may work on a version, or an option in this, to specify by length and direction of chord.

The last line you drew prior to the curve should be tangent to the curve (or description would have said "non-tangent").  Offset this line to the right, a distance equal to the curve radius. The end of the offset line will be the center of the curve. Draw a line between those endpoints, rotate that line by the central angle, this will set the end of the curve.  Draw a circle and trim to get desired curve.