Find the expression for the sight angle of a driver a `30^o` angle in terms of x. The distance between their car and the point on sidewalk is 100 ft from the intersection.
The main road in front of a school runs north/south along the east side. a side walk runs east/west along the south side of school, leading to a cross walk. A secondary school road intersects the west side of main road near the cross wall, forming a `30^o` angle with the sidewalk. For the safety of the school children using the side walk, engineers are interested in the sight angle that drivers have as they drive on the secondary road approaching this intersection.
I think what you're asking about is how to extend or "prolong" a line of sight. The method of doing this varies for a end point that is in the sight line or out of the sight line. For a sight angel that is within the line of sight, it seems you may use the Pythagorean Theorem:
l - d = l - (l2 - h2)1/2 = l - l(1 - (h/l)2)1/2