Say we have 2 pairs of associated values denoted as (x1, y1) and (x3, y3). We know a number x2, which is between x1 and x3. We need to find the corresponding value of x2, which is denoted by y2.
| x1 | y1 |
| x2 | y2 |
| x3 | y3 |
y2 can be derived as below,
| x1 | y1 |
| x2 | y2 |
| x3 | y3 |