UVa11646

题目大意： 给定跑道周长400，弯道是同一个圆的两部分（You are also told that the sliced circles will be such that they are part of the same circle.）同时，给定矩形的长宽比例a : b，求长、宽具体值

如下图：

ang1 = atan(a/b);

ang2 = PI - 2*ang1;

由 x / (2*r) = sin(ang1)     得： r = x/(2*sin(ang1));

x + ang2*（x/(2*sin(ang1))） = 200;

于是： x = 200 / (1+ang2/(2*sin(ang1));

再由 x/a = y/b  导出：y=x*b/a;