We first find A2, for which we multiply A with itself. We perform matrix multiplication in which we multiply rows of first matrix with columns of second matrix element by element and add.
Answer:
see explanation
Step-by-step explanation:
Using the trigonometric identity
sin²x + cos²x = 1 , then
sin²x = 1 - cos²x and cos²x = 1 - sin²x
Consider the left side
← expand numerator/denominator using FOIL
=
= 
= 
= 
= cot²A = right side , thus proven