Cut the Triangle in half to figure ridge height using a^2 + b^2 = c^2 method for right triangles.

17’ x 17’ x 25’5” Triangle
23’5” = 23.416’ / 2 = 11.708’
17^2 – 11.708^2 = 151.915
SQRT(151.915) = 12.325’ = Eve to Ridge Height (lower ridge)

12.325 * 11.708 = 144.306 sq ft (17’x17’ x 25’5” Triangle)

Use similar method to figure other ridge heights.