Question

1、水管的外部需要包扎,包扎时用带子缠绕在管道外部.若要使带子全部包住管道且不重叠（不考虑管道两端的情

Answer 1

画出其侧面展开图,如下图：

则：ABCD必为平行四边形,且DC = CF = AB = AG

根据已知可求得：AC = 2π

过A作BC的垂线AE,则：AE = 1,且易知：CAE = ABC = a

故可知：cos a = 1/(2π)