When solving for lengths of sides or angles in triangles, how do you know whether to use Trig Ratios, Sine Law or Cosine Law? If someone would lend a hand it’d be awesome, thanks;)

A= r2 × 3.14 11×11 ↓ ↓ 121 × 3.14 = 379.94 → 379.9

This is what i found “an explicit formula designates the nth term of the sequence, as an expression of n (where n = the term's location). it defines the sequence as a formula in terms of n. this example is an arithmetic sequence(the same number, 5, is added to each term to get to the next term).” i hope this you for what your looking for. can you plz mark me brainliest?