puzzled by <a b/c> key in home vs cas for sin(45) degrees

[Liamtoh Resu]

I am puzzled by:

In home mode , evaluating SIN(45) gives three answers when cycling it
with the <a b/c> key: the irrational fraction, a decimal approximation,
and a fractional approximation.

In cas mode, evaluating sin(45) gives the irrational fraction at first.
Cycling the <a /bc> key alternates between the decimal approximation
and the fractional approximation.

I would have thought in cas mode then <a b/c> key would also show
the irrational fraction as well.

Any feed back would be appreciated.

Thanks.