“割补”是解立体几何题的特有方法,该方法的理论根据是:“将某些直观图割补成另一些直观图,以显露原直观图的一些隐含条件”.一、割成锥例1 从空间一点 O 出发的四条射线两两所成的角都是θ,则θ一定是____.(填“锐角”、“钝角”或 “Cutting” is a unique method to solve a three-dimensional geometric problem. The theoretical basis of this method is: “Making some intuitive graphs into some other intuitive diagrams to reveal some implied conditions of the original visual ”. First, cut into a cone example 1 from the space of a point O of the four rays of the two into two angles are θ, then θ must be ____. (fill “acute angle ”, “obtuse ” or