View Compilation Error

0_0_31508101_12267.cpp: In function 'int main()':
0_0_31508101_12267.cpp:8:24: error: too few arguments to function 'double pow(double, double)'
         v =  PI * pow(r) * 4/3 ;
                        ^
In file included from 0_0_31508101_12267.cpp:2:0:
GCC4.9.2/x86_64-w64-mingw32/include/math.h:151:18: note: declared here
   double __cdecl pow(double _X,double _Y);
                  ^