Using a Sum or Difference Identity, Write the Following as an Expression

Multiple Choice

Using a sum or difference identity, write the following as an expression involving functions of x.
-Find $\cos \theta$ if $\sin \theta = - \frac { 5 } { 13 }$ and $\theta$ is in quadrant III.

A) $- \frac { 5 } { 12 }$
B) $- \frac { 12 } { 13 }$
C) $\frac { 12 } { 5 }$
D) $- \frac { 13 } { 5 }$