Question

4 ctg(11п/18) - 3 ctg(47п/18)

Answer 1

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