arccos range and domain: [−1, 1] → [0, π]
arccos takes inputs in [−1, 1] and returns angles in [0, π]. That range covers every angle a triangle can have, which is why the Law of Cosines never suffers an ambiguous case while the Law of Sines does.
Related Inverse identities
Common questions
What is the arccos range identity?
arccos takes inputs in [−1, 1] and returns angles in [0, π]. That range covers every angle a triangle can have, which is why the Law of Cosines never suffers an ambiguous case while the Law of Sines does.
Which identities are related to arccos range?
arccos range belongs to the Inverse group. The identities used alongside it most often are arcsin range and arctan range.
Practise it
Reading a formula is not the same as recalling it under time pressure. The workspace drills Inverse questions in the quiz, and the triangle solver shows a worked solution for any triangle you type in.
Or browse all 45 identities in the full reference, or read the trigonometry guides for the method behind them.