Use the Fundamental Identities to Find the Value of the Trigonometric

Multiple Choice

Use the fundamental identities to find the value of the trigonometric function.
- $\cos \omega$ , if $\tan \omega = - \frac { 2 } { 7 }$ and $\sin \omega > 0$

A) $- \frac { \sqrt { 53 } } { 7 }$
B) $\frac { 7 \sqrt { 53 } } { 53 }$
C) $\frac { \sqrt { 53 } } { 2 }$
D) $- \frac { 7 \sqrt { 53 } } { 53 }$