First of all, we should understand that the intersection of tangent and straight line and circle forms a right triangle with the center of the circle, and the length of one side is fixed equal to the radius, so the length of tangent is related to the length of hypotenuse. The shorter this side is, the shorter the tangent length is. The problem is simplified as the shortest distance from the center of the circle to the vertical, that is, the distance from the center of the circle (3,0) to the straight line y=x is d=√3, and the minimum tangent length is L 2 = D 2.

l= 1