tangent-chord angle

例句：

1. 1. The angle between the two tangents is 30 degrees.
   两个切线的夹角是30度。
2. 2. The chord of a circle is the line that connects all points on the circle.
   圆的弦是连接圆上所有点的线。
3. 3. The tangent to this curve at point A is 5 units.
   曲线在点A处的切线长度为5单位。