直接写出得数．= = == = == = == = =
过三角形的顶点A作三角形ABC底边BC的平行线和高．
过∠ABC内的一点P分别画两边的平行线，再过P点作BC的垂线．
过C点分别向AB作一条垂线和一条平行线．
如图，过直线上一点A作这条直线的垂线．
直线外一点A作一条垂直于该直线的垂线．
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