Invasion of privacy

Hello Rabbi, a few questions.
Is it permissible to study mathematics on Tisha B’Av?
The media tends to publish a lot of data about the private lives of politicians, things that of course do not concern and belong to the general public. Is there a halachic problem with this (Darby and Gershom’s ban on reading letters to others)? And given that this is forbidden even after it has been made public, will I still, as a Torah-observant and mitzvot, be a star to watch?