gmsh sinusoidal mesh density

Point (1) = {0, 0, 0};  
Point (2) = {1, 0, 0};  
Point (3) = {2, 0, 0};  
Point (5) = {1, 1, 0};  
Point (9) = {1, -1, 0}; 

Line(1) = {1, 2}; 
Line(2) = {2, 3}; 
Line(3) = {3, 5}; 
Line(5) = {5, 1}; 
Line(7) = {5, 2}; 

Line Loop(8) = {1, -7, 5}; Plane Surface (9) = {8}; 
Line Loop(10) = {7, 2, 3}; Plane Surface (11) = {10}; 

Line(12) = {1, 9}; 
Line(13) = {9, 2}; 
Line(14) = {9, 3};

Line Loop(15) = {1, -13, -12}; Plane Surface(16) = {15}; 
Line Loop(17) = {2, -14, 13}; Plane Surface(18) = {17}; 

// Sets the element size in the left region (9) 
Field[1] = MathEval; Field[1].F = "0.011+0.009*Sin(x*12)"; 

Field[6] = Restrict; Field[6].IField = 1; 
Field[6].FacesList = {16}; 
Background Field = 6;