Interact with the applet for a few minutes. [br]The [b][color=#9900ff]purple lines[/color][/b] are the [b]ALTITUDES [/b]of the triangle. [br]The [b][color=#0000ff]blue point[/color][/b] is the [b]ORTHOCENTRE[/b] of the triangle.
[i]An [b][color=#0000ff]orthocentre [/color][/b]of a triangle is ...[/i]
the point of intersection of the altitudes of a triangle.
Move the vertices of the triangle around. What happens with the orthocentre?