The point where the three "altitudes" meet. An "altitude" is a line that goes through a vertex (corner point) and is at right angles to the opposite side.

Try moving the points below, and notice:

• the orthocenter can be inside or outside of the triangle.

• also try putting the points on grid lines and see what interesting things you can discover.

Try moving the points below, and notice:

• the orthocenter can be inside or outside of the triangle.

• also try putting the points on grid lines and see what interesting things you can discover.