What is wrong with MATLAB asin() function.

I am trying to use asin in a matlab simulink model but it aslways showing this error : Domain error. To compute complex results from real x, use 'asin(complex(x))'. But when i am debugging the error i found that it is computing asin(0.5)=1.0142e-311. how this is happening in matlab.

Answer 1

[Voss]

Since both screen shots have the debugger stopped on line 5, it would appear that the value of ux is up to date but that thetad has not yet been calculated for that ux (since line 5 has not been executed for that ux).

Indeed asin(0.5) gives a different value than the thetad shown:

asin(0.5)

ans = 0.5236