The hundredth is the 3rd number after the decimal place (so the 9). Look at the number before it and if it is 5 or above then round it to the next hundredth. In this case it is only a zero so we don't change the 9 just substitute it 0's. Therefore the answer is 52,900.
If you need further help let me know, hope this helped you.

Step-by-step explanation:
We know that
cos 2x = 2cos²x - 1
So we have

Substituting 

5.4 because the 9 bumps it to 5.35.
And the 5 bumps it to 5.4.