Exercise 57 Page 478

n/a=a/■ Since we are given a right triangle, we can use a corollary of the Right Triangle Altitude Theorem, which discusses the similar right triangles inside every right triangle.

Let's compare the theorem's corollary to the known segment names of our figure. DB/CB=CB/■ ⇔ n/a=a/■ In our case, n is a partial segment of the hypotenuse and a is the length of one side of the given triangle. We can complete our proportion using the length of the hypotenuse. Looking at the given figure, we can see that this length is c.

Let's complete the given proportion! n/a=a/c