初三相似三角形的题目,急
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初三相似三角形的题目,急
如图,在△ABCD中,点D为BC上一点,点P在AD上,过P点作PM//AC交AB于点M,作PN//AB交AC于点N
(1) 若点D是BC的中点,且AP:PD=2:1,求AM:AB的值
(2) 若点D是BC的中点,试证明AM/AB =AN/AC
![](http://img.wesiedu.com/upload/f/5c/f5cd143302b9ca9e1d5d4cdf902e28ef.jpg)
如图,在△ABCD中,点D为BC上一点,点P在AD上,过P点作PM//AC交AB于点M,作PN//AB交AC于点N
(1) 若点D是BC的中点,且AP:PD=2:1,求AM:AB的值
(2) 若点D是BC的中点,试证明AM/AB =AN/AC
![](http://img.wesiedu.com/upload/f/5c/f5cd143302b9ca9e1d5d4cdf902e28ef.jpg)
![初三相似三角形的题目,急](/uploads/image/z/18530852-68-2.jpg?t=%E5%88%9D%E4%B8%89%E7%9B%B8%E4%BC%BC%E4%B8%89%E8%A7%92%E5%BD%A2%E7%9A%84%E9%A2%98%E7%9B%AE%2C%E6%80%A5)
(1)
过D作DE//PM交AB于E
AE/AB=DC/CB=1/2
AM/AE=AP/AD=2/3
故AM/AB=1/2*2/3=1/3
(2)
过D作DE//PM交AB于E
过D作DE//PN交AC于F
AE/AB=DC/CB=1/2
AM/AE=AP/AD
故AM/AB=AP/2AD
同理AN/AC=AP/2AD
故AM/AB =AN/AC
过D作DE//PM交AB于E
AE/AB=DC/CB=1/2
AM/AE=AP/AD=2/3
故AM/AB=1/2*2/3=1/3
(2)
过D作DE//PM交AB于E
过D作DE//PN交AC于F
AE/AB=DC/CB=1/2
AM/AE=AP/AD
故AM/AB=AP/2AD
同理AN/AC=AP/2AD
故AM/AB =AN/AC