âíóòðè íåãî. Äîêàçàòü, ÷òî, åñëè 6 BAO = 6 DAC, òî äèàãîíàëè ÷åòûðåõóãîëüíèêà ïåðïåíäèêóëÿð-
íû.
Ðåøåíèå. Òàê êàê 6 ABO = (π − 6 AOB)/2 = π/2 − 6 ADB, 6 DAC + 6 ADB = π/2, ÷òî ðàâíî-
ñèëüíî óòâåðæäåíèþ çàäà÷è (ðèñ.9.1).
âíóòðè íåãî. Äîêàçàòü, ÷òî, åñëè 6 BAO = 6 DAC, òî äèàãîíàëè ÷åòûðåõóãîëüíèêà ïåðïåíäèêóëÿð-
íû.
Ðåøåíèå. Òàê êàê 6 ABO = (π − 6 AOB)/2 = π/2 − 6 ADB, 6 DAC + 6 ADB = π/2, ÷òî ðàâíî-
ñèëüíî óòâåðæäåíèþ çàäà÷è (ðèñ.9.1).