生活背景树木、房屋在阳光照射写会产生影子,物体在灯光照射下会产生影子.几何抽象细直木棒AB在垂直于桌面的平行光线照射下,点A的影子是A′,点B的影子是B′,线段A′B′叫做木棒AB在桌面上的射影.实施几何抽象:线段AB与直线l在同一平面内,AA′⊥l于A′,BB′⊥l于B′,则点A′、B′叫做点A、B在直线l上的射影(投影),线段A′B′叫做线段AB在 Living background Trees, houses in the sun will produce a shadow write, the object will have a shadow in the light irradiation.Abstract geometric straight rods AB parallel to the desktop in the light irradiation, the shadow of point A is A ', the shadow of point B Is B ', the line segment A'B' is called projectile AB on the desktop. The implementation of geometric abstraction: Line AB and line l in the same plane, AA'⊥l in A ', BB'⊥l in B', then Point A ', B' is called point A, B in the projection of a straight line l (projection), the line segment A'B 'is called the line segment AB