for a right triangle with legs legnth a and b and hyptonuse c
a^2+b^2=c^2
9 feet from base, that's one leg
wire is hypotnuse, it's 1 more than height on tree
c=b+1
so
9^2+b^2=(b+1)^2
81+b^2=b^2+2b+1
minus b^2+1 from both sides
80=2b
divide both sides by 2
40=b
c=b+1
c=40+1
c=41
legnth of wire is 41ft
