Slow simulation when using asind

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Eleni.T 2020-6-11

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https://ww2.mathworks.cn/matlabcentral/answers/546404-slow-simulation-when-using-asind

评论： Eleni.T 2020-6-11

hello!

I am trying t model a sun position algorithm in simulink and i used the embedded matlab function. My simulation time is 10*3600s. The function includes:

function [altitude, azimuth]= fcn(N, SL, LL, L, LST)
    B=(N-81)*360/364;
    ET=9.87*sind(2*B)-7.53*cosd(B)-1.5*sind(B);
    AST=LST*60+ET+4*(SL-LL);
    h=(AST/60-12)*15;
    delta=(23.45*sind(360/365*(284+N)));
    altitude=asind(sind(L)*sind(delta)+cosd(L)*cosd(delta)*cosd(h));
    azimuth=asind(cosd(delta)*sind(h)/cosd(altitude));

However, when i use the 'asind' instead of 'asin' for the 'azimuth=asind(cosd(delta)*sind(h)/cosd(altitude))' equation, the simulation becomes extremely slow and i never get an answer. When i use asin I get an answer very quickly, though it is not correct since it is in radians instead of degrees. Does anyone know any potential reason for this extremely slow running?

Thank you