**Johann Müller from Königsberg** was a German mathematician and astronomer who was born on June 6, 1436 near * Königsberg* (meaning king's mountain in Latin Regiomontanus) in Germany, and died July 6 in Rome, Italy. Considered a prodigy from a young age, Johann Müller contributed significantly to trigonometry and astronomy.

In addition to establishing the study of algebra and geometry in Germany, it reactivated the study of Renaissance astronomy. He studied at the universities of Leipzig and Vienna where he studied mathematics and astronomy. In Rome, he studied Greek and philosophy, translating ancient scientific books. Back in Germany he set up a printing company and an observatory in Nuremberg to stimulate science and literature.

Back in Rome at the invitation of Pope Sixtus IV, he died suddenly, apparently killed by poisoning, as he was a vehement critic of certain currents of ecclesiastical thought. Eminent mathematician, perhaps the most influential of the fifteenth century, in 1464 published *From omnimodis triangulis*, a remarkable treatise on trigonometry that marked the revival of this branch of mathematics in Europe, which would not be printed until the next decade, in 1533.

Johann Müller, who was also known as Regiomontanus, structured his work in a similar way to the famous book Elements of the mathematician Euclid. Your work * Of triangulis * It was divided into five books, the first of which had the basic definitions of quantity, reason, equality, circles, bows, strings, and sine function. He then presented the list of axioms he would assume, along with 56 geometry theorems. Already in the second book, began the law of sine (in modern notation, not used by Regiomontanus, it is * a / sen A = b / sen B = c / sen C*) and used it to solve triangles. Books 3, 4, and 5 dealt with trigonometry in the sphere, which of course is of great importance to astronomy.

In * Tabulae directionum* (1490) emphasized the tangent function, a subject dealt with deficiency in the earlier work. In * Epitome of Almagest* emphasized the mathematical parts of Ptolemy's memorable work.

* Information obtained from the MacTutor History of Mathematics archive.