atan函数:返回数值的余切值
原型:double atan(double x)
<pre name="code" class="cpp">#include<iostream> #include<cmath> using namespace std; int main() { double PI = 4.0*atan(1.0); double r; while(cin>>r) { cout<<"PI = 4.0*atan(1.0) = "<<PI<<endl; // 求pi值 cout<<PI*r*r<<endl; int sita; sita = r; //圆的面积 cout<<tan(sita/180*PI)<<endl; //输入角度,求tan值; } return 0; }