Use method in namespace doesnt work

Question

i create game with opengl (c++) and i have namespace in file .h :

namespace SR
{
    #include "Geometric.h"
    //#include others in this namespace 
}

when i create in main.cpp some object and i call method from the object (Geometric) -> it doesnt work ,but when i erase the namespace in .h file :

//namespace SR
    //{
        #include "Geometric.h"
        //#include others in this namespace 
    //}

it work , why ?.

This is when i erase namespace from .h and call method in .cpp [its work]:

    #include "shooting_range.h"

int main(int agrc,char** agrv)
{
    Geometric p;
    p.getCoordinates();
    return 0;
}

This is when i use namespace (error : undefined reference to SR::Geometric::Geometric())

    #include "shooting_range.h"

int main(int agrc,char** agrv)
{
    SR::Geometric p;
    p.getCoordinates();
    return 0;
}

And there i try add brackets [error : error: request for member ‘getCoordinates’ in ‘p’, which is of non-class type ‘SR::Geometric()]

#include "shooting_range.h"

int main(int agrc,char** agrv)
{
    SR::Geometric p();
    p.getCoordinates();
    return 0;
}

I don't know why it doesn't work :-( My english is bad i am sorry ... I try to explain the best ... I am confused .

_________- edit : I relocate namespace to geometric.h , but still doesnt work . (request for member ‘getCoordinates’ in ‘p’, which is of non-class type ‘SR::Geometric()) Geometric.h :

#ifndef _GEOMETIC_H_
#define _GEOMETIC_H_

#include <GL/gl.h>

#define MAX_VERTEX 300

struct coordinates
{
    GLdouble x,y,z;
    GLdouble n_x,n_y,n_z;
    GLubyte r,g,b;
};

namespace SR
{


class Geometric
{
    public :
        int a;
        Geometric();

        void draw();

        void rotate(GLdouble angle,GLdouble x,GLdouble y,GLdouble z);
        void translate(GLdouble x,GLdouble y,GLdouble z);
        void scale(GLdouble x,GLdouble y,GLdouble z);

        coordinates* getCoordinates(); //get all vertex
        coordinates getCoordinates(GLint); //get data spacific vertex - if vertex == null => error

        GLboolean setCoordinates(coordinates*,GLint); //initialization all vertex through parameters
        GLboolean setCoordinates(coordinates,GLint); //change data specific vertex


    protected :
        GLshort number; //number of vertex, maximal number of vertex is macro MAX_VERTEX
        coordinates* vertex;
        GLdouble matrix[16];
};

}

#endif // _GEOMETIC_H_

Geometric.cpp

#include "Geometric.h"

SR::Geometric::Geometric()
{
    vertex = NULL;
    number = 0;
}

coordinates* SR::Geometric::getCoordinates()
{
    return vertex;
}

coordinates SR::Geometric::getCoordinates(GLint i)
{
    return vertex[i];
}

GLboolean SR::Geometric::setCoordinates(coordinates* vertex,GLint number)
{
    if(number <= 0 || number > MAX_VERTEX)
        return -1;

    if(this->vertex)
        delete[] vertex;

    this->vertex = new coordinates[number];
    this->number = number;

    for(int i = 0;i < number;i++)
    {
        this->vertex[i] = vertex[i];
    }
        return 0;
}

GLboolean SR::Geometric::setCoordinates(coordinates vertex,GLint i)
{
    if(number <= 0 || i >= this->number)
        return -1;

    this->vertex[i] = vertex;

        return 0;
}

#include "shooting_range.h"

main.cpp

int main(int agrc,char** agrv)
{
    SR::Geometric p();
    p.getCoordinates();
    return 0;
}