What is formula of cos8x
Answers
Answered by
2
Answer:
cos6x−cos8x
=2sin(
2
6x+8x
)sin(
2
8x−6x
)
=2sin7xsinx
Answered by
3
Answer:
Step-by-step explanation:
Upon applying the double-angle formula for cosine three times, we have:
cos(8x) = cos[2(4x)]
= 2cos^2(4x) - 1
= 2[2cos^2(2x) - 1]^2 - 1
= 2{2[2cos^2(x) - 1]^2 - 1}^2 - 1
= 2{2[4cos^4(x) - 4cos^2(x) + 1] - 1}^2 - 1
= 2[8cos^4(x) - 8cos^2(x) + 1]^2 - 1
= 2[64cos^8(x) - 128cos^6(x) + 80cos^4(x) - 16cos^2(x) + 1] - 1
= 128cos^8(x) - 256cos^6(x) + 160cos^4(x) - 32cos^2(x) + 1.
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