E is a point on side CB produced of an isosceles triangle ABC with AB=AC. If AD⊥BC and EF⊥AC, prove that ΔABD∼ΔECF.
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Solution
It is given that ABC is an isosceles triangle. ∴AB=AC ⇒∠ABD=∠ECF InΔABDandΔECF ∠ADB=∠EFC(Each90°) ∠BAD=∠CEF(Provedabove) ∴ΔABDΔECF(ByusingAAsimilaritycriterion)