MATLAB: Trigonometric equation solving matlab

matrixmatrix manipulationSymbolic Math Toolbox

syms a1 a2 theta1 theta2
alpha1=-(pi/2);
alpha2=0;

When i am solving the following equation in command prompt. sin(theta1)*cos(alpha1)

ans =
-(4035888341267763*sin(theta1))/9007199254740992

Now i need the output as -sin(theta1) because cos(-90) is -1. I need to round of the decimal value.

Best Answer

HUH? The solution you show in ans does not follow from what you have written above that. So it is literally impossible to know what you are doing since you have not provided useful information for us to answer.

Anyway, you need to learn to use vpa. This will resolve those long integers that the symbolic TB tends to generate.

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MATLAB: I’m not sure what is wrong with this code regarding the sin and cos function.

Like Azzi said, pi contains infinite decimal numbers, To avoid this ambiguity i recommend you to use the degree functions instead of radians cosd and sind,

 cosd(90)=0
 cos(pi/2)=6.1232e-017

MATLAB: How to solve a non-linear equation system as function handle with fsolve

qini = zeros(1,6);             % Initial guess
ci = fsolve(@funec,qini)       % fsolve with the function handle, unknown variables and initial guess
                               % done many variations here, none of them worked
function ec = funec(x);
q1 = x(1);
q2 = x(2);
q3 = x(3);
q4 = x(4);
q5 = x(5);
q6 = x(6);
ec =[...
    sin(q6)*(cos(q1)*cos(q2)*sin(q3)*sin(q4) - cos(q4)*sin(q1) + cos(q1)*cos(q3)*sin(q2)*sin(q4)) - cos(q6)*(cos(q2 + q3)*cos(q1)*sin(q5) + cos(q5)*sin(q1)*sin(q4) + cos(q1)*cos(q2)*cos(q4)*cos(q5)*sin(q3) + cos(q1)*cos(q3)*cos(q4)*cos(q5)*sin(q2)) - 3097002709122497/18014398509481984
    cos(q6)*(cos(q1)*cos(q4) + cos(q2)*sin(q1)*sin(q3)*sin(q4) + cos(q3)*sin(q1)*sin(q2)*sin(q4)) + sin(q6)*(cos(q2 + q3)*sin(q1)*sin(q5) - cos(q1)*cos(q5)*sin(q4) + cos(q2)*cos(q4)*cos(q5)*sin(q1)*sin(q3) + cos(q3)*cos(q4)*cos(q5)*sin(q1)*sin(q2)) - 6124274932042799/36028797018963968
    - sin(q2 + q3)*cos(q5) - cos(q2 + q3)*cos(q4)*sin(q5) - 139701203459709/140737488355328
    70*cos(q1) + 360*cos(q1)*sin(q2) - 65*sin(q1)*sin(q4)*sin(q5) + 380*cos(q1)*cos(q2)*cos(q3) - 380*cos(q1)*sin(q2)*sin(q3) + 65*cos(q1)*cos(q2)*cos(q3)*cos(q5) - 65*cos(q1)*cos(q5)*sin(q2)*sin(q3) - 65*cos(q1)*cos(q2)*cos(q4)*sin(q3)*sin(q5) - 65*cos(q1)*cos(q3)*cos(q4)*sin(q2)*sin(q5) + 19869/50
    sin(q6)*(cos(q1)*cos(q4) + cos(q2)*sin(q1)*sin(q3)*sin(q4) + cos(q3)*sin(q1)*sin(q2)*sin(q4)) - cos(q6)*(cos(q2 + q3)*sin(q1)*sin(q5) - cos(q1)*cos(q5)*sin(q4) + cos(q2)*cos(q4)*cos(q5)*sin(q1)*sin(q3) + cos(q3)*cos(q4)*cos(q5)*sin(q1)*sin(q2)) + 2202239090516653/2251799813685248
    cos(q2 + q3)*cos(q6)*sin(q4) - sin(q6)*(sin(q2 + q3)*sin(q5) - cos(q2 + q3)*cos(q4)*cos(q5)) + 7591943296130745/288230376151711744
    cos(q2 + q3)*cos(q1)*cos(q5) - sin(q5)*(sin(q1)*sin(q4) + cos(q1)*cos(q2)*cos(q4)*sin(q3) + cos(q1)*cos(q3)*cos(q4)*sin(q2)) - 102014544375725/18014398509481984
    70*sin(q1) + 360*sin(q1)*sin(q2) - 380*sin(q1)*sin(q2)*sin(q3) + 380*cos(q2)*cos(q3)*sin(q1) + 65*cos(q1)*sin(q4)*sin(q5) + 65*cos(q2)*cos(q3)*cos(q5)*sin(q1) - 65*cos(q5)*sin(q1)*sin(q2)*sin(q3) - 65*cos(q2)*cos(q4)*sin(q1)*sin(q3)*sin(q5) - 65*cos(q3)*cos(q4)*sin(q1)*sin(q2)*sin(q5) - 1563/20
    cos(q6)*(sin(q2 + q3)*sin(q5) - cos(q2 + q3)*cos(q4)*cos(q5)) + cos(q2 + q3)*sin(q4)*sin(q6) - 2129854249224409/18014398509481984
    cos(q6)*(cos(q1)*cos(q2)*sin(q3)*sin(q4) - cos(q4)*sin(q1) + cos(q1)*cos(q3)*sin(q2)*sin(q4)) + sin(q6)*(cos(q2 + q3)*cos(q1)*sin(q5) + cos(q5)*sin(q1)*sin(q4) + cos(q1)*cos(q2)*cos(q4)*cos(q5)*sin(q3) + cos(q1)*cos(q3)*cos(q4)*cos(q5)*sin(q2)) - 8872946535830847/9007199254740992
    cos(q2 + q3)*cos(q5)*sin(q1) - sin(q5)*(cos(q2)*cos(q4)*sin(q1)*sin(q3) - cos(q1)*sin(q4) + cos(q3)*cos(q4)*sin(q1)*sin(q2)) - 8718732974408059/72057594037927936
    360*cos(q2) - 380*cos(q2)*sin(q3) - 380*cos(q3)*sin(q2) - 65*cos(q2)*cos(q5)*sin(q3) - 65*cos(q3)*cos(q5)*sin(q2) - 65*cos(q2)*cos(q3)*cos(q4)*sin(q5) + 65*cos(q4)*sin(q2)*sin(q3)*sin(q5) - 39571/100];
end

Best Answer

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