



 
Hi REnu, I can help you with the first task, expressing R in terms of r. In my diagram $Z$ is the centre of the circle $K$ and $S$ and $T$ are the centres of circles $A$ and $B.$ $M$ is the midpoint of the line segment $ST.$ The length $TQ = r$ and the length $ZQ = R$ so if you can express the length $ZT$ in terms of $r$ you have what you need. What is the measure of the angle $SZT?$ What is the measure of the angle $MZT?$ What is the measure of the angle $TMZ?$ $MT = r.$ What is the length $ZT?$ Penny
 


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