The total no. of solution of x in [0, 5p...

The total no. of solution of x in `[0, 5pi]` satisfy the equation `3(cos 2x) – 10 cos x + 7 = 0` is :-

A

5

B

6

C

8

D

7

Verified by Experts

The correct Answer is:

C

`3(2cos^(2)x-1)-10cos x + 7 = 0`
`6 cos^(2)x-10cos x+4 = 0`
`(3 cos x - 2) [2 cos x - 2] =0`
`therefore cos x = 2//3, 1`

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