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If alpha is a root of 25 cos^2 theta+ 5 ...

If `alpha` is a root of `25 cos^2 theta+ 5 cos theta- 12 = 0,pi/2 < alpha< pi`, then `sin 2 alpha` is equal to :

A

`24/25`

B

`-24/25`

C

`13/18`

D

`-13/18`.

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