Write me a working program in C, with this info, The saying ``You can't see the wood for the trees'' is not only a cliche, but is also
incorrect. The real problem is that you can't see the trees for the wood. If you stand in the
middle of a ``wood'' (in NZ terms, a patch of bush), the trees tend to obscure each other
and the number of distinct trees you can actually see is quite small. This is especially true
if the trees are planted in rows and columns (as in a pine plantation), because they tend to
line up. The purpose of this problem is to find how many distinct trees you can see from
an arbitrary point in a pine plantation (assumed to stretch ``for ever'').
You can only see a distinct tree if no part of its trunk is obscured by a nearer tree--that is
if both sides of the trunk can be seen, with a discernible gap between them and the trunks
of all trees closer to you. Also, you can't see a tree if it is apparently ``too small''. For
definiteness, ``not too small'' and ``discernible gap'' will mean that the angle subtended at
your eye is greater than 0.01 degrees (you are assumed to use one eye for observing).
Thus the two trees marked obscure at least the trees marked from the given view
point.
Write a program that will determine the number of trees visible under these assumptions,
given the diameter of the trees, and the coordinates of a viewing position. Because the
grid is infinite, the origin is unimportant, and the coordinates will be numbers between 0
and 1.
Input
Input will consist of a series of lines, each line containing three real numbers of the form
0.nn. The first number will be the trunk diameter--all trees will be assumed to be
cylinders of exactly this diameter, with their centres placed exactly on the points of a
rectangular grid with a spacing of one unit. The next two numbers will be the x and y
coordinates of the observer. To avoid potential problems, say by being too close to a tree,
we will guarantee that diameter≤x,y≤(1-diameter). To avoid problems with trees being
too small you may assume that diameter
0.1. The file will be terminated by a line
consisting of three zeroes.
Output
Output will consist of a series of lines, one for each line of the input. Each line will
consist of the number of trees of the given size, visible from the given position.
Sample input
0.10 0.46 0.38
0 0 0
Sample output
128, please make sure it's working, this is how the idea works, this could help you, "Since the limited opening angle is above 0.01, the trees that are too far away are not considered, so a part of the trees can be exhausted.

For the trees at the exhaustive position, the numbers from the current position are arranged from small to large, and start to consider whether there are trees in the front, so first calculate the opening angle [l, r] of each tree, and then for a tree, find out whether Shaded by trees that are closer.

For the part of calculating the opening angle (a point outside the circle), there are two ways

Calculate the intersection of the two tangents to obtain the angle formed by the two intersections, and ensure that it does not exceed 180 degrees.
Pull from the starting point to the center of the circle, after calculating the angle, according to the triangle formed by the tangent, calculate asin and superimpose the angle."