If
show that F(x) . F(y) = F(x + y).
Given : 
To show : F(x) . F(y) = F(x + y).
Formula used : 
If A is a matrix of order a
b and B is a matrix of order c
d ,then matrix AB exists and is of order a
d ,if and only if b = c
F(x) = 
F(y) = 
F(x + y) = 
F(x) . F(y) =
. 
= 
F(x) . F(y) = 
We know that,
cosx(cosy) – sinx (siny) = cos(x+y) and -cosx(siny) - sinx(cosy) = -sin(x+y)
F(x) . F(y) = 
F(x + y) = F(x) . F(y) = 
F(x + y) = F(x) . F(y)