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If cos9x-2cos6x=2, then general solution of x is?
Kindly explain the whole procedure. 
8 months ago

Answers : (2)

Arun
21973 Points
							
cos6x = 2 (cos3x) ^ 2 - 1 
cos9x = 4 (cos3x) ^ 3 - 3 (cos3x). 

Cos3x considered t = (| T | =

==> 4T ^ 3 - 4T ^ 2 - 3T + 2 = 2 

==> T = 0; 
T = -1/2 
T = 3/2 (by type> 1) 

$ * $ With cos 3x = 0 ==> 3x = (Pi) / 2 + k (Pi) ==> x = (Pi) / 6 + k (Pi) / 3 

$ * $ With cos 3x = -1/2 ==> 3x = - (P) / 3 + k2 (Pi) ==> x = - (P) / 9 + k2 (Pi) / 3 
8 months ago
Kavya Singh
8 Points
							
The options were:-
a) 2kπ+--/6     b) 2π/9(3n+-1)
c)2nπ+--/3       d)x€¢
The cprreco option in this according to solution will be which one and how?
8 months ago
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