C
r
D⃗
O
||C−(O+D⃗ t)||||(C−O)−D⃗ t||||OC→−D⃗ t||||OC→−D⃗ t||2(OC→−D⃗ t)⋅(OC→−D⃗ t)OC→⋅OC→−2t(D⃗ ⋅OC→)+(D⃗ ⋅D⃗ )t2||D⃗ ||²t2−2(D⃗ ⋅OC→)t+(||OC→||2−r2)twhere: abc=r=r=r, where OC→=C−O=r2=r2=r2=0=−b±sqrt(b2−4ac)2a=||D⃗ ||²,=2(D⃗ ⋅OC→),=||OC→||2−r2