cos 6x = 32 cos x - 48cos4 x + 18 cosx - 1
Answers
Answered by
13
Answer:
LHS = cos6x
= cos3(2x)
use, the formula,
cos3A = 4cos³A - 3cosA
= 4cos³(2x) - 3cos(2x)
use the formula,
cos2A = 2cos²A -1
= 4(2cos²x-1)³ - 3(2cos²x-1)
= 4{8cos^6x -3.(2cos²x)².1 +3.2cos²x.1² - 1 }-6cos²x +3
= 32cos^6x -48cos⁴x + 24cos²x -4 -6cos²x + 3
= 32cos^6x - 48cos⁴x +18cos²x -1 = RHS
Similar questions