Answer:
Step-by-step explanation:
cos(2a) = cos^2(a) - sin^2(a)
cos(2a) = 2cos^(a) - 1
cos(2a) = 11/25
11/25 = 2 cos^(a) - 1 Add 1 to both sides
1 + 11/25 = 2 cos^2
25/25 + 11/25 = 2 cos^2(a)
36/25 = 2 cos^2 (a) Divide by 2
36/50 = cos^2 (a) Take the square root of both sides.
6/5*sqrt(2) = cos(a)
