In the following figure, 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........(i)
In ΔABDandΔECF, ∠ADB=∠EFC(Each90∘) ∠ABD=∠ECF (from (i)) ∴ΔABD∼ΔECF (By using AAA similarity criterion)