COS(X) dislpay wrong answer

[Albert Chan]

I was curious of how Prime round the 53 bits float to its internal 48-bits mantissa.
Can someone with a Prime try this for me ? (CAS mode)

sin(3.0) * 2^50 - 158887e9

With IEEE 53-bits mantissa float, I get 3928234.84375

Will Prime store the chopped mantissa, result of 3928234 ?
Or, will it stored better rounded 48 bits, result of 3928235 ?