Question 34416
Draw the ladder on a sheet, the hypotenuse is the lenght of the ladder. The base angle is 72deg.

{{{ Sin 72 = height of building the ladder reaches/length of ladder }}}
 
use a calc to get sin 72 ( works out to .951 )

so, height of the building = 10 * .951 = 9.51 ft

for the distance to the side of the building, use the cosine of the angle

{{{ cos 72 = distance to the side of the building / height of ladder }}}

cos 72 = .309

so,distance to the side of the building = 10 * .309 = 3.09 ft

In such 'ladder' probems, a sketch is a great help :-))