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In the Given Figure, Express a in Terms of B. - Mathematics

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Question

In the given figure, express a in terms of b.

Sum

Solution

In Δ ABC,

BC = BA

∴ ∠BCA = ∠BAC
and Ext. ∠CBE = ∠BCA + ∠BAC

⇒ a = ∠BCA + ∠BCA

⇒ a = 2 ∠BCA .........(i)

But ∠ACB = 180° − b ..........(∵ ∠ACD and ∠ACB are linear pair)

⇒ ∠BCA = 180° − b .............(ii)

∴ a = 2 ∠BCA = 2 (180° − b)

= 360°− 2b

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Chapter 15: Triangles - Exercise 15 (B)

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Selina Concise Mathematics [English] Class 7 ICSE
Chapter 15 Triangles
Exercise 15 (B) | Q 11
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