Directions: Question based on the following paragraph. |
If\[\cos \frac{\pi }{7},\cos \frac{3\pi }{7},\cos \frac{5\pi }{7}.\]are the roots of the equation \[8{{x}^{3}}-4{{x}^{b}}-4x+1=0\]. |
A) 2
B) 4
C) 8
D) None of these
Correct Answer: B
Solution :
Since, \[\sec \frac{\pi }{7},\sec \frac{3\pi }{7},\sec \frac{5\pi }{7}\] are the roots of Eq.(ii) \[\therefore \]\[\sec \frac{\pi }{7}+\sec \frac{3\pi }{7}+\sec \frac{5\pi }{7}=4\]You need to login to perform this action.
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