### Theory:

An altitude of a triangle is the perpendicular line drawn from the vertex of the triangle to the opposite side.  The altitude of a triangle is also known as the height of the triangle.

In triangle $$ABC$$, $$AD$$ is the altitude which is a perpendicular line drawn from the vertex $$A$$ to the point $$D$$ in the opposite side $$BC$$.

Important!
• The altitude makes a right angle with the base of a triangle. Here in $\mathrm{\Delta }$ $$ABC$$, $$AD$$ is perpendicular to $$BC$$.
• As there are three possible vertices for any triangles, there will be three possible altitudes.