Question

Why is it that the orthocenter of an obtuse triangle must lie on the outside of the triangle?

Answer 1

It is important to understand the meaning of orthocenter in respect to a triangle first. Ii is actually the intersection of all the altitudes within a triangle. The altitudes can be drawn from an angle to the opposite side but the line should create a right angle with the side of the triangle. In case of obtuse triangle, the three lines would meet outside the triangle. I hope the answer helps.