退化二次曲线的过其外一点的切线

Tangents Passing through the Point Not on a Degenerate Quadric Curve

对退化二次曲线Γ过不在Γ上的一点M0的切线的各种情况进行了讨论,证明了Γ有奇点时,过M0的切线一般总要经过Γ的奇点.

This paper generally discusses the tangent equation of a degenerate quadratic curve Γ,where the tangent passes through an arbitrary point M_0 on R^2 plane. The paper also proves that when Γ has a singular point C, the tangent must pass through C.