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《中学数学教学》2 0 0 2年第 4期擂题 ( 5 6)第 3题是 :图 1如图 1所示 ,求证。( 1 )A1、A2 、A3、A4 四点共圆的充要条件是 :RA1·RA3-RA2 ·RA4 =QA1·QA4 -QA2 ·QA3;( 2 )A1、A2 、A3、A4 四点共圆或A2 A4 平分A1A3的充要条件是 :PA3·PA4 -PA1·PA2 =QA1·QA4 -QA2 ·QA3
“Middle school mathematics teaching” in 2002 fourth issue (5 6) The third question is: Figure 1 shown in Figure 1, verify. (1) The necessary and sufficient conditions for the four-point co-circulation of A1, A2, A3, and A4 are: RA1·RA3-RA2 ·RA4 =QA1·QA4 -QA2 ·QA3; (2) A1, A2, A3, A4 four-point circular Or A2 A4 is a sufficient and necessary condition for dividing A1A3: PA3·PA4 -PA1·PA2 =QA1·QA4 -QA2 ·QA3