orthocentre 垂心有乜用???

圖片參考：http://upload.wikimedia.org/wikipedia/commons/thumb/9/93/Triangle.Orthocenter.svg/182px-Triangle.Orthocenter.svg.png



An altitude of a triangle is a straight line through a vertex and perpendicular to (i.e. forming a right angle with) the opposite side. This opposite side is called the base of the altitude, and the point where the altitude intersects the base (or its extension) is called the foot of the altitude. The length of the altitude is the distance between the base and the vertex. The three altitudes intersect in a single point, called the orthocenter (垂心) of the triangle. The orthocenter (垂心) lies inside the triangle if and only if the triangle is acute.
The three vertices together with the orthocenter (垂心) are said to form an orthocentric system.








請參考網:
http://en.wikipedia.org/wiki/Triangle_%28geometry%29
http://en.wikipedia.org/wiki/Orthocentric_system



2007-11-20 15:33:00 補充：
O.K.嗎?

三角形的三條高所在直線相交於一點，該點稱為三角形的垂心。對銳角(鈍角)三角形來說，垂心位於三角形內(外)，而直角三角形的垂心即為直角頂點。H常用來表示三角形ABC的垂心。