a straight line or plane that touches a curve or curved surface at a point but does not intersect it at that point
ratio of the opposite to the adjacent side of a right-angled triangle
Some examples are given by inscribed and circumscribed circles ofpolygons, lines intersecting and tangent toconic sections, thePappusandMenelausconfigurations of points and lines. 一些例子所给予者和限制各界的多边形，线相交和相切的圆锥部分，帕普斯和墨涅拉俄斯配置的点和线。
The graph of a concave function is always below its tangent. 一个凹函数的图象总在它的切线的下方。
Both of approaching and returning movements are along the tangent of the circle. 绕转之后移动方向为自南向北，也是沿圆周的切线运动。
The tangent may be used to find the direction. 这方向也可用正切求得。
Store normals in generic space, e.g., Tangent Space. 存储非普通空间的法向量，例如，正切空间。
The earth,..without flying off in a tangent line, constantly rolls about the sun.
出自： G. Berkeley
The radiation is emitted tangent to these trajectories.