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一、题目2010年辽宁省高考数学理科卷第12题:有四根长都为2的直铁条,若再选两根长都为a的直铁条,使这6根直铁条端点处相连能够焊接成一个三棱锥形的铁架,则a的取值范围是__.教学中有学生1给出如下解答:解这6根铁条焊接成的三棱锥有且只有两种可能情况(如图1、图2).(1)如图1,设E为BC的中点,连结EA、ED。则EA⊥BC,ED⊥BC,∴∠AED为二面角A-BC-D的平面角,
First, the subject 2010 Liaoning Province Mathematical Sciences Volume 12: There are four long two straight iron bar, if the election of two long as a straight bar, so that the six straight bar at the end point Connected to be able to be welded into a triangular pyramid frame, the range of a is __. Teaching students 1 gives the following solution: solution of the six iron rods welded into the triangular pyramid There are only two possible situations (Figure 1, Figure 2) (1) As shown in Figure 1, let E be the midpoint of BC, connecting EA and ED. EA ⊥ BC, ED ⊥ BC, ∴∠ AED plane angle of the dihedral angle A-BC-D,