Sorry for my bad English ;)
the line that is || the side of length 6 is right. the triangles bottom sides length is 10 (32-22=10)

So you get a triangle with sides 6 8 10 these numbers are specific for a triangle with 90*. to get the height u firstly need to get the triangles square. square = 6*8/2.
And finally the height = 2*square/a . Where a = 10.
If the triangle you got is without the 90* corner then the formula for its square is S=sqrt(p(p-a)(p-b)(p-c)) the formula is called Heron formula. And p = (a+b+c)/2 a,b,c are the sides of the triangle