#### So which side is the base?

Any side of the triangle *can* be a base. All that matters is that the base and the height must be perpendicular.

Any side can be a base, but every base has only one height. The height is the line from the opposite vertex and perpendicular to the base. The illustration below shows how any leg of the triangle can be a base and the height always extends from the vertex of the opposite side and is perpendicular to the base. Play around with our applet to see how the area of a triangle can be computed from any base/height pairing.

The picture below shows you that the height can actually extend outside of the triangle. So technically the height does not necessarily intersect with the base.