Question 297337
The rafters form a triangle with the base angles 36 and the peak angle 180-72=108
If we drop  a line from the peak angle to the middle of the house that is at 16 feet 

We have a right triangle with one leg 16.
We have angles 36 90 and 54

the hypotenuse will be the length of the roof from the peak to the 36 degree angle.
so we have the base as 16 and the hypotenuse
we have hypotenuse and adjacent (16) and angle 36
After you calculate the rising rafter, be sure to add 2 feet.