"disappointed to know" is correct and can be used in written English.
This phrase expresses a feeling of disappointment upon learning something. Example: I was disappointed to know that my favorite restaurant closed down permanently.
'It's incredible.' 'Just amazing - uh-may-zeeng,' says a senior London producer, looking disappointed to know that the UK rights to the show seem more or less sewn up.
'A significant number of women we have consulted would be very disappointed to know that the Government is pushing for this,' said Baroness Uddin, the Labour peer who co-chaired a Home Office inquiry on forced marriage.
Since it is a matter of choice, it is open season for these latter; but they will perhaps be disappointed to know that I'm not offended by what they say, but on the contrary feel a certain warm sympathy towards them, for one would wish fuller lives for all.
Mainsbridge said he was particularly disappointed at the Soil Association's response, which was that it could not guarantee milk with its label would not be from within the cull zones: "Organic produce is already seen as having higher animal welfare standards, so I think a lot of their customers will be surprised – and disappointed – to know that organic milk may come from cull farms".
I'm sure we'll run tomorrow". If you're just tuning in to read about some red hot qualifying action, you'll be disappointed to know that all we have is grey, tepid non-existent action.
"I am very disappointed... to know that record companies may be attempting these kinds of shenanigans". SoundScan Chief Executive Mike Shalett acknowledged that the company has found troubling anomalies in record sales data.
She had won 42 consecutive 100-meter finals since 1997, but if her time was a bit slower than usual or the race a bit closer than usual, people were disappointed and wanted to know what was wrong.
"Whenever they come to Britain they give them the warmest welcome you can imagine, so people will be very, very disappointed and disheartened to know that these two guys now are under a huge cloud of suspicion.
"I am angry, I am disappointed and I want to know what they are going to do about it," she said.
Ouch! Photograph: Kim Ludbrook/EPA Updated at 1.58pm BST 12.33pm BST Andy Schleck is out of the Tour Sad news here: Andy Schleck (@andy_schleck) Very disappointed to let you know that i will not be able to start.
