To find sin(a) and ctg(a) where a = 1/2, we can follow these steps:

sin(a) = sin(1/2)
Using a calculator, we find that sin(1/2) is approximately 0.4794.

ctg(a) = ctg(1/2)
Using the identity ctg(a) = 1/tan(a), we can rewrite ctg(1/2) as 1/tan(1/2).
Using a calculator, we find that tan(1/2) is approximately 0.5463.
Therefore, ctg(1/2) = 1/0.5463 ≈ 1.8305

So, sin(a) is approximately 0.4794 and ctg(a) is approximately 1.8305.