You can't reason with an angry cat, talk them around or comfort them. You need to give them the space to resolve whatever has angered them, while trying to figure out what it is. If there is another cat in the household, this is most likely the culprit, whether it meant to be or not. Cats are relatively solitary animals and sometimes the presence of another cat or animal simply gets on their nerves. Kids can also cause a similar effect if they pester the cat excessively. An angry cat is also a dangerous one and is more likely to lash out with claws or bite a hand. Therefore, don't try to pet them or get close to them and give them an escape route from the room to avoid conflict.