As shown in the figure, in the regular pentagon ABCDE, ab = AE, BC = ed, angle B = angle e, and point F is the midpoint of CD

As shown in the figure, in the regular pentagon ABCDE, ab = AE, BC = ed, angle B = angle e, and point F is the midpoint of CD

AF ⊥ CD
Connect AC and AD
In △ ABC and △ AED,
∵AB=AE,∠B=∠E,BC=ED,
∴△ABC≌△AED.(SAS)
∴AC=AD.
∵ f is the midpoint of CD,
∴AF⊥CD.