Function to find the length of the direct common tangent
def lengtang ( r1 , r2 , d ) : NEW_LINE INDENT print ( " The ▁ length ▁ of ▁ the ▁ direct ▁ common ▁ tangent ▁ is " , ( ( ( d ** 2 ) - ( ( r1 - r2 ) ** 2 ) ) ** ( 1 / 2 ) ) ) ; NEW_LINE DEDENT