(Solved): pls help 5. If \( \sec (x)=-1 \) and \( \frac{\pi}{2} \leq x \leq \pi \), determine the exact values ...

5. If \( \sec (x)=-1 \) and \( \frac{\pi}{2} \leq x \leq \pi \), determine the exact values of Hall-Angle Formulas a) \( \sin \left(\frac{x}{2}\right) \) \( \sin \left(\frac{x}{2}\right)=\pm \sqrt{\frac{1-\cos (x)}{2}} \) \( \cos \left(\frac{x}{2}\right)=\pm \sqrt{\frac{1+\cos (x)}{2}} \) \( \tan \left(\frac{x}{2}\right)=\pm \sqrt{\frac{1-\cos (x)}{1+\cos (x)}} \) b) \( \cos \left(\frac{x}{2}\right) \) c) \( \tan \left(\frac{x}{2}\right) \)