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Most Important Selected Qs for JEE AdvancedMathematicsCircle

Let S be a circle of radius 1 with centre at A . Two circles with radius r and R and centre at C and D are externally tangent to each other and internally tangent to S . If D A C=120^ , find the value of R r+3 R+3 r .

Correct answer

3

Step-by-step solution

aligned & & 120^ & = (1-r)^2+(1-R)^2-(r+R)^2 2(1-r)(1-R) =- 1 2 & & 3-3 R-3 r-r R & =0 & & R r+3 R+3 r & =3 aligned

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