 1BPD 2(SĐ BD - SĐAC),  1AQC 2(SĐ BD + SĐAC)  BPD AQC  = SĐ BD = 1400  700BCDB) HS TỰ CHỨNG MINH

5. a) Ta có:  1BPD 2(sđ BD - sđAC),  1AQC 2(sđ BD + sđAC)  BPD AQC  = sđ BD = 140

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 70

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BCDb) HS tự chứng minh