(Solved): Let ???????????? be any triangle. Let ????, ????, and ???? be the altitudes of ???????? ...
Let ????????????? be any triangle. Let ?????, ?????, and ????? be the altitudes of ????????????? and let ???? be the inradius of the triangle.
Prove that 1
?????
+ 1
?????
+ 1
?????
= 1
????.