Use Identities to Find the Indicated Value for Each Angle $\cos 2 \theta = \frac { 4 } { 5 }$

Use identities to find the indicated value for each angle measure.
- $\cos 2 \theta = \frac { 4 } { 5 }$ and $\theta$ terminates in quadrant III $\quad$ Find $\cos \theta$ .

A) $\cos \theta = - \frac { 3 \sqrt { 10 } } { 10 }$

B) $\cos \theta = - \frac { \sqrt { 10 } } { 3 }$

C) $\cos \theta = \frac { 3 \sqrt { 10 } } { 10 }$

D) $\cos \theta = 0$

Correct Answer:

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