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.
