Respuesta :

amna04352

Answer:

-7/18

Step-by-step explanation:

cos(2x) = 1 - 2sin²x

cos(2x) = 1 - 2(5/6)²

= 1 - 2(25/36)

= 1 - 25/18

= -7/18

Larrysammz

Answer:

±√(11/18)

Step-by-step explanation:

sinx = 5/6

  • applying the trigonometric rule sin²x + cos²x = 1
  • so to get cos²x = 1- sin²x

sinx = 5/6

sin²x = (5/6)² = 25/36

  • 1-sin²x = 1-25/36 = 36-25 /36 = 11/36

  • cos ²x = 11/36

cos x = ±√(11/36)

cos 2x = 2 x±√(11/36) = ±√(11/18)