In what field did Nicolaus Copernicus obtain his doctorate?

Leonardo da Vinci. Leonardo spent his last years in France at the home awarded him by Francis I. He brought three mas­ter­pieces: Mona Lisa, The Virgin and Child with St. Anne and St. John the Baptist.

In Vinci. Leonardo da Vinci was born on 15 April 1452, in a farm­house about 3 kilo­me­ters from the town of Vinci, near Flo­rence. His full name was "Leonar­do di ser Piero da Vinci", which means "Leonar­do, son of Piero, of Vinci".

By mirror writing. Leonar­do's writings are mostly in mir­ror-im­age cursive. The reason may have been more a prac­ti­cal ex­pe­di­en­cy than for reasons of secrecy as is often sug­gest­ed. Since Leonardo wrote with his left hand, it is probable that it was easier for him to write from right to left.

A positive number . Negative number raised to even, positive power (e.g. -3 raised to power 2,4,6) is always a positive number.