qline l1 0 0 10 20
qline l2 0 0 10 -40
qline l3 160 0 -40 10
circ2d3Tan tan1 l1 l2 l3

checklength tan1_1 -l 213.09795279419643
checklength tan1_2 -l 284.90187851033369
checklength tan1_3 -l 131.38343888467227
checklength tan1_4 -l 63.235238531994284