__cos b = 1/2 [cos (a+b) + cos (a-b)]
a. sin(a)
b. sin(b)
c. cos(a)
d. cos(b)

cos(a)

Step-by-step explanation:

I substituted it on a calculator:

a = 30

b = 45

1/2 [ cos (a + b) + cos (a - b)]

1/2 [ cos (30 + 45) + cos (30 - 45)] = Sqrt6/4

cos(a)cos(b)

cos(30)cos(45) = Sqrt6/4

C is correct

COS (A) is right

Step-by-step explanation:

see explanation

step-by-step explanation:

since the sequence is geometric there is a common ratio r between consecutive terms, that is

r = 4 ÷ - 2 = - 2

r = - 8 ÷ 4 = - 2

r = 16 ÷ 8 = - 2

the next term - 13 must be incorrect as it should be - 32 for the sequence to be geometric.

the first 4 terms are therefore geometric with common ratio r = - 2

stop cheating

step-by-step explanation: