unknown function的用法和樣例：
例句
- On the first problem of a class of the second order parabolic systems of two variables and two unknown functions.
一類二階兩個自變數兩個未知函數的拋物形方程組的第一問題。 - A very simple method is to uselinear interpolation, which assumes that the unknown function is linear between every pair of successive points.
一個非常簡單的方法是使用線性插值，它假定未知函數的線性每對之間的連續點。
