the computer catch the position of target such as (x,y), (maybe a3), and calculate the a1 and a2, draw module with them in the screen.
input: the target position(x,y)
output: the 3 angles(a1,a2)
float A,B,C; //temp variables
float x,y; //input
float a1,a2; //output
A = -2 * x * L1;
B = 2 * (y-L3)*L1;
C = sq(L2) - sq(L1) - sq(x) - sq(y-L3);
a1 = 2*atan((B-sqrt(sq(B)+sq(A)-sq(C)))/(A+C))
A = 2 * (y-L3) * L2;
B = 2 * x * L2;
C = sq(L2) + sq(x) + sq(L3 - y) - sq(L1) ;
a2 =2*atan((B-sqrt(sq(B)+sq(A)-sq(C)))/(A+C))