Mein Versuch:
y = R-1/2*sqrt(4R2-S2) | -R | *(-1)
R-y = 1/2*sqrt(4R2-S2) | *2
2(R-y) = sqrt(4R2-S2) | ^2
4(R-y)2 = (4R2-S2)
4(R2-2Ry+y2) = (4R2-S2)
4R2-8Ry+4y2 = 4R2-S2 | -4R2
-8Ry+4y2 = -S2 | *(-1)
8Ry-4y2 = S2 | +- sqrt
+- sqrt(8Ry-4y2) = S
