What I did in this diagram is I computed the efficient portfolio frontier-- now it's the blue line with three assets.

在这张图表中,我计算了有效边界-,蓝色线表示三种资产的组合。

耶鲁公开课 - 金融市场课程节选

The pink line here is the efficient portfolio frontier when we have only stocks and bonds to invest.

这条粉色曲线就是有效边界,这个投资组合只包括了股票和债券。

耶鲁公开课 - 金融市场课程节选

But when that's not true, then there is a typical sort of modern frontier, a land bridge which there a line is-a theoretical line is drawn through it, and on one side is one city, and the other side is another city.

但还不止这些天然边界,另外还有种边界形式,和现代国境线很类似,是由一座陆桥,分割出一条界线…假象的界线,界线的一边是一个城邦,另一边是另一个城邦

耶鲁公开课 - 古希腊历史简介课程节选

That means that you want to pick, ultimately, a point on this-- this line is tangent to the efficient portfolio frontier with all the other assets in it.

那意味着你会最终会在这上面选一个点-,这条直线是与有效边界相切的,后者包含了所有的资产组合。

耶鲁公开课 - 金融市场课程节选

If we want to add that asset to the portfolio, what it does is it produces an efficient portfolio frontier that is now a straight line; I show that on the diagram.

如果我们将其加入到投资组合中去，则会生成一条资产组合的有效边界,即一条直线;,我在图里把它画出来了。

耶鲁公开课 - 金融市场课程节选

Tangent means that it has the same slope, it just touches the efficient portfolio frontier for risky assets at one point, and the slope of the efficient portfolio frontier, including the riskless asset, is a straight line that goes through the tangency point, here.

相切意味着斜率相同，它与包含风险资产的有效边界,交与一点，而包含无风险资产的，有效边界，则是一条过切点的直线，切点在这里。

耶鲁公开课 - 金融市场课程节选