Length of the direct common tangent between two externally touching circles | Function to find the length of the direct common tangent ; Driver code
< ? php function lengtang ( $ r1 , $ r2 ) { echo " The ▁ length ▁ of ▁ the ▁ " , " direct ▁ common ▁ tangent ▁ is ▁ " , 2 * sqrt ( $ r1 * $ r2 ) ; } $ r1 = 5 ; $ r2 = 9 ; lengtang ( $ r1 , $ r2 ) ; ? >