Question

初二数学求大神帮忙解答！

Answer 1

答案见图

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7、选C【解析： ∵∠DAC+∠C=90°，∠DAC+∠AFE=90°

                           ∴∠C=∠AFE

                        又∵∠BFD=∠AFE

                           ∴∠C=∠BFD

                        又∵∠FBD+∠BFD=90°

                            ∴∠FBD=∠DAC

                        又∵∠ABC=45°

                           ∴BD=AD

                           在△BFD和△ACD中

                           ∠BFD=∠C,

                           ∠FBD=∠DAC，

                           BD=AD,

                           ∴△BFD≌△ACD(AAS)

                           ∴BF=AC=8cm】

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