First, we will draw a diagram to understand better the question
so we will use a trigonometric function called the tangent because is the trigonometric function that has as a quotient the opposite leg and the adjacent leg of a triangle in order to obtain how long is the shadow
x is the length of the shadow
![\tan (60)=(15)/(x)](https://img.qammunity.org/2023/formulas/mathematics/college/4p8cpa7o0dyqzfsa6u5dwq8p0i8l6colte.png)
then we need to isolate the x
![x=(15)/(\tan (60))=8.66](https://img.qammunity.org/2023/formulas/mathematics/college/u8clpzf5pzy0qnfs89jhvkwgrsrlmz3mre.png)
the shadow is 8.66 ft long