Cos² 2x = (1+cos 4x )/2
cos² 6x = (1+cos 12x)/2
subtract to get 1/2 (cos 4x - cos 12x )
= 1/2 (2 sin 4x sin 8x ) as cos A - cos B = 2 [ sin (A+B)/2 sin (A-B)/2 ]
so the answer
Answer:the 57th term is 78
Step-by-step explanation:
The sequence is an arithmetic sequence. The formula for determining the nth term of an arithmetic sequence is expressed as
Tn = a + (n - 1)d
Where
a represents the first term of the sequence.
d represents the common difference.
n represents the number of terms in the sequence.
From the information given,
a = - 6
d =3/2
n = 57
We want to determine the value if the 57th term, T57. Therefore,
T57 = - 6 + (57 - 1) ×3/2
T57 = - 6 + 56 × 3/2 = - 6 + 84
T57 = 78
Answer:
= 4/15
Step-by-step explanation:
=4 . 2/5 /6
= 4/15