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Two circles of radius 1 and 4 touch each...

Two circles of radius 1 and 4 touch each other externally. Another circle of radius r touches both circles externally and also one direct common tangent of the two circles. Then `[1/r]=`

Text Solution

Verified by Experts

`In/_BFO`
`OB^2=BF^2+OF^2`
`(r+4)^2=(4-r)^2+(d-x)^2`
`(d-r)^2=(x+4)^2-(4-r)^2`
`=r^2+16+8r-16-r^2+8r`
`=16r`
`d-x=4sqrtr-(1)`
`In/_OCE`
...
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