～學(xué)北師大七級下數(shù)學(xué)暑假作業(yè)(四)含答案-資料下載頁
2025-01-18 07:21本頁面
【正文】 CD∴DE∥AC14．證明：∵BF⊥AC，∴∠AFB＝∠CFB＝90176?！唷螩＋∠CBF＝90176。∵AB＝AC，點D是BC的中點，∴AD⊥BC∴∠ADC＝90176?！唷螩＋∠CAD＝90176?！唷螩BF＝∠CAD∵∠AFB＝90176。, ∠BAC＝45176。,∴∠AFB＝45176?！唷螧AC＝∠AFB∴AF＝BF.又∵∠CBF＝∠CAD, ∠AFB＝∠CFB＝90176。,∴△AEF≌△BCF．15．解:PC＝PD.理由: 過點P作PE⊥OA于點E,作PF⊥OB于點F∵OM平分∠AOB∴PE＝PF∵∠AOB＝∠PEO＝∠PFO＝90176?！唷螮PF＝90176。又∵∠CPD＝90176?！唷螩PE＝∠DPF又∵∠PEC＝∠PFD＝90176。, PE＝PF∴△PCE≌PDF∴PC＝PD
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