Why does the "simple" function in the Symbolic Math Toolbox cause MATLAB to hang when trying to simplify my expression?

I have created the following expression using symbolic variables:

>> syms x y z a b c iu iv su sv; 
>> x_hat = cos(iv)*( cos(su)*sin(sv)*z - sin(su)*sin(sv)*y + cos(sv)*x +a ) ... 
- sin(iv)*( cos(su)*cos(sv)*z - sin(su)*cos(sv)*y - sin(sv)*x +b ) ; 
>> y_hat = cos(iu)*( sin(su)*z + cos(su)*y + c ) ... 
- sin(iu)*sin(iv)*( cos(su)*sin(sv)*z - sin(su)*sin(sv)*y - cos(sv)*x +b ) ... 
- sin(iu)*cos(iv)*( cos(su)*cos(sv)*z - sin(su)*cos(sv)*y - sin(sv)*x +a ) ;

When I try to simplify this expression with the "simple" function, it produces a lot of output to the Command Window, but remains 'Busy' and does not yield a simplified expression. How can I fix this?

>> simple(diff(atan( x_hat / y_hat ),x))

Answer 1

[MathWorks Support Team]

The use of 'simple' function is no longer supported. Instead, you should use the "simplify" function, which works much faster on this example and does yield a simplified form of the expression.