their nervous systems and ability to produce baby birds, and can lead to kidney(肾) failures and death. So condors with high levels of lead are sent to Los Angeles Zoo, where they are treated with calcium EDTA, a chemical that removes lead from the blood over several days. This work is starting to pay off. The annual death rate for adult condors has dropped from 38% in 2000 to 5.4% in 2011. 6.4.2多边形的外角和
导学案
学习目标
1.理解和掌握多边形外角和定理的推导过程； 2. 能进行多边形内角和、外角和定理的综合运用. 一.自学释疑
1.一个多边形的一个顶点处，可作有几个外角，它们是什么关系？
2.在四边形的四个内角中，最多能有几个钝角？最多能有几个锐角？
二.合作探究 探究点一
问题1：小明沿一个五边形广场周围的小跑，按逆时针方向跑步.
their nervous systems and ability to produce baby birds, and can lead to kidney(肾) failures and death. So condors with high levels of lead are sent to Los Angeles Zoo, where they are treated with calcium EDTA, a chemical that removes lead from the blood over several days. This work is starting to pay off. The annual death rate for adult condors has dropped from 38% in 2000 to 5.4% in 2011.
(1)小明每从一条街道转到下一条街道时，跑步方向改变的哪个角？在图中标出.
(2)他每跑完一圈，身体转过的角度之和是多少？
(3)在上图中，你能求出∠1+∠2+∠3+∠4+∠5吗？你是怎样得到的？ 小明的推理：
问题2：如果广场是六边形、八边形、n边形那会什么结果？ 探究点二
问题1：过平面内一点O分别作与五边形ABCDE各边平行的射线OA′、OB′、OC′、OD′、OE′， 得到∠α、∠β、∠γ、∠δ、∠θ,∠1+∠2＋∠3＋∠4＋∠5是多少度？
their nervous systems and ability to produce baby birds, and can lead to kidney(肾) failures and death. So condors with high levels of lead are sent to Los Angeles Zoo, where they are treated with calcium EDTA, a chemical that removes lead from the blood over several days. This work is starting to pay off. The annual death rate for adult condors has dropped from 38% in 2000 to 5.4% in 2011.
问题2：归纳 多边形的外角：
多边形的外角和：
多边形的外角和： 探究点三
问题1：已知一个多边形,它的内角和等于外角和的3倍,求这个多边形的边数和对角线的条数?
问题2：如图，四边形ABCD中，∠B=∠D=90°，AE平分∠BAD，若AE∥CF，∠BCF=60°，请你求出∠DCF的度数．并说明你的理由．