Answer:
cos (A - B) = cos 6 x
Step-by-step explanation:
given equation,
= cos 8 x . cos 2 x - sin 8 x . sin 2 x
using identity
cos (A - B) = cos (A) . cos(B) - sin (A) . sin(B)...................(1)
cos 8 x . cos 2 x - sin 8 x . sin 2 x......................................(2)
comparing both the equation (1) and (2)
we get ,
A = 8 x B = 2 x
hence, from the above identity we can see that
cos (A - B) = cos (8 x - 2 x)
cos (A - B) = cos 6 x
