What is the formula of the sum of cubes? That is, it can calculate the third power of 1 + the third power of 2 + the third power of 3 What's the best one?
1^3+2^3+3^3+...n^3
=1/4*n^2(n+1)^2
Adjoint matrix formula of second order matrix
The main switch and the auxiliary switch
Note: Main --- > main diagonal; sub --- > sub diagonal
What is the rotation transformation formula of second order matrix
cosx -sinx
sinx cosx