The maximum line of sight distance between a transmitting and a receiving TV tower is given by the formula D equals the square root of two times R times h, where R is the radius of the earth and h is the height of the towers. When the heights of both towers are doubled, the new distance becomes the square root of two times R times two h, which simplifies to the square root of two times the square root of two R h. By substituting the original distance D, the new maximum distance is the square root of two times D.