当前位置:问百书>百科知识>如图,在正方形$ABCD$的边$BC$的延长线上取一点$E$,使$CE=AC$,连接$AE$交$CD$于$F$,则$\angle AFC$等于( )A. $112.5^{\circ}$B. $120^{\circ}$C. $135^{\circ}$D. $145^{\circ}$

如图,在正方形$ABCD$的边$BC$的延长线上取一点$E$,使$CE=AC$,连接$AE$交$CD$于$F$,则$\angle AFC$等于( )A. $112.5^{\circ}$B. $120^{\circ}$C. $135^{\circ}$D. $145^{\circ}$

2023-06-26 11:52:10 编辑:join 浏览量:620

如图,在正方形$ABCD$的边$BC$的延长线上取一点$E$,使$CE=AC$,连接$AE$交$CD$于$F$,则$\angle AFC$等于(  )A. $112.5^{\circ}$B. $120^{\circ}$C. $135^{\circ}$D. $145^{\circ}$

$\because $四边形$ABCD$为正方形,

$\therefore \angle ACD=90^{\circ}$,

$\therefore \angle DCE=90^{\circ}$,

又$\because AC$是正方形$ABCD$的对角线,

$\therefore \angle ACF=45^{\circ}$,

$\therefore \angle ACE=\angle DCE+\angle ACF=135^{\circ}$,

$\because CE=CA$,

$\therefore \angle FAC=\angle E=\frac{1}{2}(180^{\circ}-135^{\circ})=22.5^{\circ}$

$\therefore \angle AFD=\angle FAC+\angle ACF=22.5^{\circ}+45^{\circ}=67.5^{\circ}$,

$\therefore \angle AFC=180^{\circ}-67.5^{\circ}=112.5^{\circ}$,

故选:$A$.

标签:circ,ABCD,BC

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