Georg Mohr
Jørgen Mohr was a Danish mathematician, known for being the first to prove the Mohr–Mascheroni theorem, which states that any geometric construction which can be done with compass and straightedge can also be done with compasses alone.
1 April 1640
Born on the same birth day (1 April): C. Ganesha Iyer • Christian Vietoris • David Gilliland • Harlow Rothert • Jan Blokhuijsen • Jane Adams (actress, born 1965) • Lev Lobodin • Melville Shavelson • Ruth Beitia • Samboy Lim • Vitorino Antunes • Wallace Beery
Born in the same month (April 1640): Gaspar Sanz