Trigonometry
Which of the following expressions is equivalent to tanπ7+tanπ41−tanπ7tanπ4\frac{\tan\frac{\pi}{7}+\tan\frac{\pi}{4}}{1-\tan\frac{\pi}{7}\tan\frac{\pi}{4}}1−tan7πtan4πtan7π+tan4π?
sin11π28\sin\frac{11\pi}{28}sin2811π
cos3π28\cos\frac{3\pi}{28}cos283π
cos11π28\cos\frac{11\pi}{28}cos2811π
tan11π28\tan\frac{11\pi}{28}tan2811π