How to get calculation results when pi is used as a symbolic object?

When pi is used as a symbolic object, it seems that we can't get calculation results, for example:

>> syms pi;
>> cos(pi/9)

ans =

cos(pi/9)

But it isn't always that way:

>> syms pi;
>> cos(pi/2)

ans =

0

Now the question is how to get the calculation results after a symbolic expression with pi is created.

Please help me. Thank you!

Answer 1

[Star Strider]

Using vpa or double (link at the end of the vpa page) come quickly to mind.