Question

4 ctg(11п/18) - 3 ctg(47п/18)

Answer 1

$4ctg \frac{11\pi }{18} -3ctg \frac{47\pi }{18} =4ctg \frac{11\pi }{18} -3ctg(2\pi + \frac{11\pi }{18} )=\\\\=4ctg \frac{11\pi }{18} -3ctg \frac{11\pi }{18} =ctg \frac{11\pi }{18}$