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4. Show that in an isosceles triangle, angles opposite to equal sides are equal. |
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Answer» Answer: Proof: Consider an isosceles triangle ABC where AC = BC. We need to PROVE that the angles opposite to the sides AC and BC are equal, that is, ∠CAB = ∠CBA. We first DRAW a bisector of ∠ACB and name it as CD. Now in ∆ACD and ∆BCD we have, AC = BC (Given) ∠ACD = ∠BCD (By construction) CD = CD (Common to both) Thus, ∆ACD ≅∆BCD (By SAS congruence CRITERION) So, ∠CAB = ∠CBA (By CPCT) Hence proved. In an isosceles triangle, angles opposite to equal sides are equal. |
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