Hey guys my uncle is a landscaper and he has a problem for me to solve.

He has a house on a hill. The hills bottom is at the left and it ascends to the right. He has the height of that and at the top of the hill it stops ascending.
Well now you have to imagine that hill as a triangle


The only bit of the triangle he knows is the hills lengtht which he has measured. He wants to know the height of the hill. So with only one measurement of the triangle I have to figure out something before I can use my triginomatiry calculator.
I thought that the easiest angle to figure out would be the one at the top.
The top right angle. Remembering that this is real life not a triangle that you can use a ruler or triangle. I then took the approach of making it into a rectangle.




So if I could figure out the angle with the top right of the angle joining on the triangle then I could figure out the angle in the triangle and figure out the height

Any ideas how to get a pricise measurement using the rectangle or any other way?