Euler equation is widely used. 1755, the Swiss mathematician Euler first proposed this equation in his book General Principles of Fluid Motion.
Euler equation is a differential expression of functional extreme conditions. By solving the Euler equation of the functional, we can get the standing function that makes the functional extreme, and turn the variational problem into a differential problem.
concept
Everyone who has studied middle school mathematics is familiar with equations; There are various equations in elementary mathematics, such as linear equation, quadratic equation, higher order equation, exponential equation, logarithmic equation, trigonometric equation, equation and so on.
These equations are to find out the relationship between the known number and the unknown number in the studied problem, list one or more equations containing one unknown number or several unknown numbers, and then find out the solutions of the equations.
However, in practical work, there are often some problems that are completely different from the above equations. For example, if a substance moves and changes under certain conditions, it is necessary to seek the law of its movement and change; When an object falls freely under the action of gravity, it is necessary to seek the law that the falling distance changes with time.
When a rocket flies in space driven by an engine, it needs to seek its orbit, and so on. The formal resolution function should be obtained from the existing data, rather than using the known function to calculate the specific unknowns.