From the given right triangle CD is the altitude.
\In a triangle, the measure of an altitude drawn from the vertex of right angle to its hypotenuse
\is the geometric mean between the measures of the two segments of the hypotenuse.
\So, the measure of the altitude CD is the geometric mean of BD and DA.
Find the geometric mean of BD and DA.
\Geometric mean is positive number x of two positive numbers where the proportion
\a : x = x : b is true. The proportion can be written as fractions .
Write the proportion from the definition of geometric mean.
\ (Substitute
)
(Apply cross product property)
(Multiply: