Respuesta :

Answer:

Below in bold.

Step-by-step explanation:

sin ^2x + cos ^2 x = 1, so

cos^2x = 1 - (5/11)^2 = 96/121

cos x = √96/11

= 4√6/11.

sin 2x = 2 sinx cosx  = 2 * 5/11 * 4√6/11.

= 40√6/121.

cos2x =  2cos^2 x - 1

= 2 * 96/121 - 1

=  192/121 - 121/121

= 71/121.