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Question
If the base of an isosceles triangle is produced on both sides, prove that the exterior angles so formed are equal to each other.
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Solution
ED is a straight line segment and B and C are points on it.
`⇒∠EBC = ∠BCD = straight angle = 180^@``
⇒∠EBA+∠ABC = ∠ACB +∠ACD
⇒∠EBA = ∠ACD +=ACB -∠ABC
⇒∠EBA=∠ACD [From (1) ∠ABC =∠ACD]
⇒∠ABE = ∠ACD
∴Hence proved
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