Answer: the altitude is 12.04 units
Explanation:
An isosceles triangle is a triangle which has two equal sides and two equal angles. The diagram of the isosceles triangle is shown in the attached diagram. The two equal sides are 9 units each. The isosceles triangle ABC forms two right angle triangle ACF and BCF. The base AB is 16 units.
We want to determine the altitude, CF. We will apply Pythagoras theorem
Hypotenuse^2 = opposite^2 + adjacent ^2
Hypotenuse = 9
Adjacent = 16/2 = 8
Opposite = CF
9^2 = 8^2 + CF^2
CF^2 = 81 + 64 = 145
CF = √145 = 12.04