A circle is inscribed in a triangle ABC touching the side AB at D such that AD =5, BD=3. If angle A is 60o then find length BC.

Dear student,

Tangents drawn from external point to a circle are equal in lengthBD = BF=3CF =CEAD=5=AEusing cos A = b2+c2-a22bccos 60° = AE+CE2+AD+BD2-BF+CF22AE+CEAD+BD12= 5+CE2+5+32-3+CE225+CE812= 25+CE2+10CE+64-9-CE2-6CE25+CE812= 4CE+80165+CE165+CE=8CE+16025+CE=CE+20CE = 10=CFthen, BC = CF+BF=10+3=13 units


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