Given two similar triangles, what would you need to know to find an unknown length? How would you find that unknown length?

What would you need to know to find an unknown length?

For this case you need to know three measurements.

Two measures of the triangle that is similar and a measure of the original triangle.

Thus, the fourth measure is what will be the unknown side and is the one that we must find.

How would you find that unknown length?

Let:

a, b, c: known sides

x: unknown side

By similarity of triangles we have:

x / a = b / c

From here, we clear the value of the unknown side