Answer:

Explanation:
We know that
. Rounding the value of b as asked in the problem gives b=12.
From the right-triangle definition of cosine, b must be the adjacent side to the angle 22.6º and the hypothenuse of the triangle must be 3.
Then, a is the opposite side of the angle 22.6º therefore using the definition of sine,
. Solving for a, we obtain
.
We conclude that
.