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If cos3x+sin(2x-(7pi)/6)=-2 , then x is ...

If `cos3x+sin(2x-(7pi)/6)=-2` , then `x` is equal to `(k in Z)` `pi/3(6k+1)` (b) `pi/3(6k-1)` `pi/3(2k+1)` (d) none of these

A

`pi/3 (6k+1)`

B

`pi/3 (6k-1)`

C

`pi/3 (2k+1)`

D

none of these

Text Solution

Verified by Experts

The correct Answer is:
D
`cos 3x+sin (2x-(7 pi)/6)=-2`
`:. Cos 3x=-1` and `sin (2x -(7pi)/6)=-1`
or `3x=(2n+1) pi and 2x-(7pi)/6=-pi/2+2 m pi , m, n in Z`
or `x=(2n pi)/3+pi/3 and x=mpi+pi/3`
or `x=2 kpi +pi/3, k in Z`.
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