Euler 1744 + Lagrange 1755: stationary points of integral functional J[y] = integral L(x, y, y') dx satisfy d/dx(dL/dy') - dL/dy = 0; foundation of variational principles in physics.
Euler 1744 + Lagrange 1755: stationary points of integral functional J[y] = integral L(x, y, y') dx satisfy d/dx(dL/dy') - dL/dy = 0; foundation of variational principles in physics.