In mathematical operations, the method of reducing the exponent of the unknown term is called descending order.

The reduction formula is as follows:

cos2α=2cos？ α- 1= 1-2sin？ αcos？ α=( 1/2)( 1+cos 2α)sin？ α=( 1/2)( 1-cos2α)

The way to reduce the exponent of the unknown term is called descending order?

By order reduction, high-order equations (groups) can be transformed into low-order equations (groups), thus making it easier to solve equations (groups).

Common methods of order reduction include collocation method, method of substitution method, double angle method, cosine formula method, method of substitution method, derivative method, period method (the property of imaginary unit I), logarithm method, Dimov formula method (the triangular form of complex number) and so on.

Simplifying the complex is the embodiment of the principle of simplicity, and its main means are sorting, eliminating and reducing. The specific methods of dimensionality reduction and reduction include addition, subtraction, elimination of split terms, and use of reduction formulas.