Mersenne’s laws mathematically determine how to tune string instruments. Galileo had the idea first but Mersenne proved the laws experimentally. Mersenne’s laws govern the construction and operation of string instruments, such as pianos and harps.
The cartesian coordinate system unified geometry and algebra for the first time. Cartesian coordinates established a basis for calculus. A cartesian coordinate is a system used to display a specified point defined in a plane by a set of numerical coordinates.
Blaise Pascal invented the first mechanical calculator to save his father time and improve accuracy. But it was and commercial failure but its promise inspired others to attempt to improve it for over 200 years.
Blaise Pascal is best known for developing Pascal’s Law.