First you need to use the Pythagorean theorem (a²+b²=c²). Let's use 39 feet as a and 15 as b. c is the answer. So we have 39² + 15² =c². Now find what the ² 's equal. 1521+225=1746. Now square root 1746. Which will equal 41.7851648316. I will round it to the nearest whole number. 42. If you need it rounded to nearest 10th then it will be 41.8.
