Question:
Solution:
By definition:

You can divide by cos² x:

now, solving for theta, we get:
![\sec (\theta)=\pm\sqrt[]{tan^2(\theta)+1}](https://img.qammunity.org/2023/formulas/mathematics/college/28zvz77j2eykcp3hra6agd9vhg3p05p486.png)
According to this and the data of the problem, this is equivalent to:
![\sec (\theta)=\pm\sqrt[]{(12)/(11)}](https://img.qammunity.org/2023/formulas/mathematics/college/2hjrl3w2nzqqru79q53e25a8h6rsc4d97s.png)
Note that the minus sign is because the angle is in the third quadrant. So that, we can conclude that the correct answer is:
![\sec (\theta)=-\sqrt[]{(12)/(11)}](https://img.qammunity.org/2023/formulas/mathematics/college/u2nwy5uy6cpnzul2egq2zgwx4slgjwk0cz.png)