12dbsplinecurve b1 3 5 0 4 1 1 2 1 3 1 4 4 0 0 1 1 0.5 0.8 2 1 1 2 2 0.7 3 1.5 0.6 4 1.5 1 5 2 1 22dcvalue b1 2.0 x y dx dy 3set delta 0.01 4point p1 x y 5set dyvalue [dval dy] 6repeat 100 { 7 cmovetangent b1 2.0 x y dx $dyvalue 1 8 set dyvalue [expr $dyvalue + $delta ] 9 repaint 10} 11copy b1 result 12checklength result -l 6.6492776719511806