sin error invee sin error

I have a angle : float 180. I've converted it to rad angle * Mathf.DegToRad; Im trying to get the sin, cos and InvSin. cos is fine -1 but sin is wrong Im getting -8.742278E-08, and inverse is giving me an error. the code is as follows id appreciate any help as i am new to this. Thanks

  function MatrixOp (theta : float, axis : String){
 
     var op = mO();
     
     print(theta);
     //setup
     op.angleInRad = theta * Mathf.Deg2Rad;
     print("angleInRad " + op.angleInRad);
     
     op.cosQ = Mathf.Cos(op.angleInRad);
     print("cos " + op.cosQ);
 //returns right answer
     
     op.sinQ = Mathf.Sin(op.angleInRad);
     print("sin " + op.sinQ);
 //returns wrong answer    
     op.inverseSinAngle = Mathf.Asin(op.angleInRad);
     print("inversSin " + op.inverseSinAngle);
 
 //returns error 
 }