You are incorrect. Your method multiplies 57% by the current payout - this would mean that we now get 57% of the blocks we did before in a given time period. This means the mining rate is (1/0.57)-1 = 75% slower, which conincides with a 75% increase in difficulty.

Here is the correct calculation:

average time = difficulty * 2**32 / hashrate (straight from bitcoin wiki)

Hashrate is constant, only variable is difficulty. So in calculating increase in time per block for a difficulty we can simplify this to:

delta (avg. time) = delta (difficulty)

If difficulty is 57% more, then average time per block is 57% more. So if it took 1 day to get a block before, now it takes 1.57 days. Thus, your payout per day is now 1 block / 1.57 days or .636 blocks/day. Or in our case, payout was 1.146 BTC per day, it is now 1.146/1.57 = 0.73 BTC per day.

In the future it'd be good if you didn't insult before you knew you were right...