a tangent line的用法和样例：
- The procedure used to define the derivative has a geometric interpretation which leads in a natural way to the idea of a tangent line to a curve.
- The CML is derived by drawing a tangent line from the intercept point on the efficient frontier to the point where the expected return equals the risk-free rate of return.
- It's not easy to follow her think because she's always go off at a tangent.
- The Necessary Condition to Draw a Tangent Line from the Conic Section
- Don't fly off at a tangent, stick to the subject.
- Don't fly off at a tangent,stick to the subject.