LA5 marksYear: 2023HardCBSE Class 10
circlestangentincirclearea
Question
A triangle ABC is drawn to circumscribe a circle of radius 4 cm such that the segments BD and DC are of lengths 10 cm and 8 cm respectively. Find the lengths of the sides AB and AC, if it is given that area △ABC=90 cm2.

Solution
1

Triangle ABC with incircle, tangent points D, E, F and side lengths labeled with variable x
+1.5 marks2
Join OA, OB, OC and draw OE⊥AC and OF⊥AB.
BF=10 cm, CE=8 cm, Let AF=AE=x
+1.5 marks3
ar △ABC = ar △BOC + ar △COA + ar △AOB
90=21×4×(BC+CA+AB)
90=2(18+8+x+10+x)
+1 mark4
90=4(18+x)⇒x=4.5
AB=10+4.5=14.5 cm and AC=8+4.5=12.5 cm
+1 mark