Trying to set Mesh.tangents = Vector4[] gives error of "An object reference is required to access non-static member `Create_Mesh.mesh'"

hello everyone, so im following this tutorial on creating a deformable mesh, and aproximately 36 mitutes in the guy creates a function to calculate the tangents, everything seems to work fine for him but i get this error that says "An object reference is required to access non-static member `Create_Mesh.mesh'" clueless of what did I do wrong i thought you guys might have an idea on what it could be. this is the part where the problem seems to be:

     private static void RecalculateTangents (Mesh objMesh)
     {
         int [] triangles = objMesh.triangles;
         Vector3 [] vertices = objMesh.vertices;
         Vector2 [] uv = objMesh.uv;
         Vector3 [] normals = objMesh.normals;
 
         int triangleCount = triangles.Length;
         int vertexCount = vertices.Length;
 
         Vector3 [] tan1 = new Vector3[vertexCount];
         Vector3 [] tan2 = new Vector3[vertexCount];
 
         Vector4 [] tangents = new Vector4[vertexCount];
 
         for (long a = 0 ; a < triangleCount ; a++)
         {
             long i1 = triangles[a + 0];
             long i2 = triangles[a + 1];
             long i3 = triangles[a + 2];
 
             Vector3 v1 = vertices[i1];
             Vector3 v2 = vertices[i2];
             Vector3 v3 = vertices[i3];
 
             Vector2 w1 = uv[i1];
             Vector2 w2 = uv[i2];
             Vector2 w3 = uv[i3];
 
             float x1 = v2.x - v1.x;
             float x2 = v3.x - v1.x;
 
             float y1 = v2.y - v1.y;
             float y2 = v3.y - v1.y;
 
             float z1 = v2.z - v1.z;
             float z2 = v3.z - v1.z;
 
             float s1 = w2.x - w1.x;
             float s2 = w3.x - w1.x;
             
             float t1 = w2.y - w1.y;
             float t2 = w3.y - w1.y;
 
             float div = s1 * t2 - s2 * t1;
             float r = div == 0.0f ? 0.0f : 1.0f / div;
 
             Vector3 sdir = new Vector3 ((t2 * x1 - t1 * x2) * r, (t2 * y1 + t1 * y2) * r, (t2 * z1 - t1 * z2) * r);
             Vector3 tdir = new Vector3 ((s1 * x2 - s2 * x1) * r, (s1 * y2 - s2 * y1) * r, (s1 * z2 - s2 * z1) * r);
 
             tan1[i1] += sdir;
             tan1[i2] += sdir;
             tan1[i3] += sdir;
 
             tan2[i1] += tdir;
             tan2[i2] += tdir;
             tan2[i3] += tdir;
         }
 
         for (long a = 0; a < vertexCount; a ++)
         {
             Vector3 n = normals[a];
             Vector3 t = tan1[a];
 
             Vector3.OrthoNormalize(ref n, ref t);
             tangents[a].x = t.x;
             tangents[a].y = t.y;
             tangents[a].z = t.z;
 
             tangents[a].w =  (Vector3.Dot(Vector3.Cross(n, t), tan2[a]) < 0.0f) ? -1.0f : 1.0f;    
         }
 
         mesh.tangents = tangents;
 
     }

I apreciate your time and thanks a lot in advanced.