Question 57 Answer and Explanation _ACT April 2010 Form 68G Math Section

Question 57 Answer and Explanation _ACT April 2010 Form 68G Math Section

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57. If cos x = $-\frac{1}{3}$ , what is the value of cos 2x ?

(Note: (cos x)² = $\frac{1+cos\,2x}{2}$ )

A. $-\frac{8}{9}$

B. $-\frac{7}{9}$

C. $-\frac{1}{6}$

D. $\frac{1}{9}$

E. $\frac{1}{6}$

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation