Answer:
C) [tex]-\frac{47}{49}[/tex]
Step-by-step explanation:
By the cos double angle formula, we know [tex]\cos(2\theta)=2\cos^2\theta-1.[/tex] Substituting [tex]\cos \theta[/tex] into the formula, we get
[tex]\cos(2\theta)=2(-\frac{1}{7})^2-1\\~~~~~~~~~~=\frac{2}{49}-1\\~~~~~~~~~~=\boxed{-\frac{47}{49}}[/tex].
The answer is C.
