Will that tree hit my house?

Yesterday my dad and I set about sawing down a large alder tree that was leaning and looking precarious.  It was tricky to see whether it was tall enough to hit the house when it fell, but luckily some similar triangles came to the rescue.
I folded a 45º angle in a piece of scrap paper and walked to the side of the house closest to the tree. Sighting up the hypotenuse, I noticed that the topmost branches were still in view – so the tree was taller than the distance between its base and the house. 2-DSC04284
I used a guide rope attached to another tree to prevent it from falling too close the house, so my windows remained intact.  The main problem was that the chainsaw got stuck as we were cutting the notch, so we had to hack at it with an axe for awhile. Warning: the video below is not educational: