Chapter 2 - Matrices - 2.2 Properties of Matrix Operations - 2.2 Exercises - Page 60: 52

$$A^{20}=\left[\begin{array}{ccc}{1} &{0} &{0}\\{0}& {1}&{0}\\{0}&{0}&{1} \end{array}\right].$$

Given $$A=\left[\begin{array}{ccc}{1} &{0} &{0}\\{0}& {-1}&{0}\\{0}&{0}&{1} \end{array}\right].$$ Then, $$A^{20}=\left[\begin{array}{ccc}{1} &{0} &{0}\\{0}& {1}&{0}\\{0}&{0}&{1} \end{array}\right].$$