Respuesta :

princegn
cotxcos2x = 2cotx
cos2x = 2cotx/cotx
cos2x = 2
cos2x = 2cos²x - 1
2cos²x - 1 = 2
2cos²x = 2+1
2cos²x = 3
cos²x = 3/2
√cos²x = plus minus √(3/2)
cosx = plus minus √(3/2)
Panoyin
cot(x)cos(2x) = 2cot(x)
      cot(x)           cot(x)
         cos(2x) = 2

It is undefined.