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我们知道:在圆中一条弦(在弦的同侧)所对的圆周角大于圆外角.本文将利用这个性质先证明一个定理,再举例说明该定理的应用.图1定理如图1,若PA⊥平面ABC,则∠BAC∠BPC.证明作△ABC外接圆,又因为BPBA,CPCA,所以若将△PBC翻折到与△ABC共面,则A点在圆上,P点必在圆外,且A点、P点?
We know that the circle angle of a string in the circle (on the same side of the string) is greater than the outer angle of the circle. This article will use this property to first prove a theorem, and then illustrate the application of the theorem. The theorem of Figure 1 is shown in Figure 1. PA ⊥ plane ABC, ∠ BAC ∠ BPC. Prove △ ABC circumcircle, but also because BPBA, CPCA, so if the △ PBC folded to △ ABC coplanar, then A point in the circle, P point must be in the circle Outside, and A, P?