@ARTICLE {, title = {How massive is the black hole at the centre of our Galaxy?}, author = {Křížek, Filip and Křížek, Michal and Šolc, Jakub}, journal = {Obzory matematiky, fyziky a informatiky}, year = {2007}, volume = {36}, number = {1}, pages = {43--51}, issn = {1335-4981}, abstract = {Using the formula for calculation of roots of a quadratic equation, Pythagorean theorem, Kepler's laws and observed data, we show that the mass of the black hole at the centre of our Galaxy is more than 3 million Sun masses. }, }