c#中的math类

http://wenku.baidu.com/link?url=TliiVtdB8IeO3wiM9mVSD-3wLZcLum7dsXlEZgSKawo6x-qvE_G3VL_yDa3ZQ_9ZFlGGwdK0hRZMza-uQll_hF3MhNFLcCRwx99t2untlRO