What is the formula for the volume of a sphere

What is the formula for the volume of a sphere

In the first method, the volume formula of a sphere can be derived from tetrahedron http://tsmschool.com/Laojialeyuan/WebBook/gao/0/0245b/245b_ jxkp_ 2.htm
The second method -- the limit method derivation of the spherical volume formula
http://www.gdmzzx.com/jszy/shuxuewu/ztyj/tjgs.doc