Possible isosceles triangle/area?

Hey, new here to this forum and thought I would give it a shot.

I have 2 measurements of a triangle and need to find the height. I believe the 2 sides are at a 45* angle but could not be sure.

Base measures 56 ft. & one side measures 45 ft.

This would be really easy if I only knew the height but was unable to reach it from a ladder. This is to determine roof area on a really tall building. Probably really easy for most of you here.

Thanks for any help. John

Have determined that both sides are 45 and base is 56. How is height determined??? Searched old posts but to no avail.