The illustration of the program is shown in the figure. The missing value is the length of the shadow, that is the base of the right triangle. Since the figure is a right triangle, we can use the pythagorean theorems
c^2 = a^2 + b^2
where c is the longest length or the hypotenuse and a and b are the other two shorter legs. Let's denote the length of the shadow as 'a'.
a = √(c^2 - b^2)
a = √(36^2 - 35^2)\
a = √71 = 8.43 m