每次用时都错,先是提示
`sqrt' undeclared (first use this function) (Each undeclared identifier is reported only once for each function it appears in.) 好像说第一次用未声明
然后声明了又说
[Linker error] undefined reference to `sqrt(int)' ld returned 1 exit status
难道还要定义不成?
到底该怎样申明啊?