Question

find the general solution of class11th ques.​

Answer 1

Answer:

cos 3x + cos x - cos 2x                            = 0 

[cos 3x + cos x ] - cos 2x                         = 0 

2 cos [(3x + x)/2] .cos [(3x-x)/2] - cos 2x = 0 

2 cos 2x . cos x  - cos 2x                         = 0 

cos 2x  [ 2 cos  x  - 1 ]                             = 0 

cos 2x  = 0  or cos x = 1/2 = cos π/3

2x = (2n +1 )π/2 or x = 2mπ +- π/3

x = (2n + 1 ) π/4 or x = 2mπ +- π/3 ;

where  n , m ∈ I

Answer 2

GOOD NIGHT!!

1) Cos A + Cos B = 2 Cos (A + B)/2 × Cos (A - B)/2

2) Cos ß = Cos y

ß = 2nπ ± y ( General Solution )

n € Z

QNO:-1

Cos 3x + Cos x - Cos 2x = 0

2 Cos 2x × Cos x - Cos 2x = 0

Cos 2x ( 2 Cos x - 1 ) = 0

Cos 2x = 0 OR 2 Cos x = 1

Cos 2x = Cos 90 OR Cos x = Cos 60

2x = 2nπ ± 90 OR x = 2nπ ± 60

x = nπ ± 45 OR x = 2nπ ± 60