Identifier: Trig Function Category 3

The only real identifier for this specific case is seeing a fraction with  $1–\mathit{cos}\left(\mathrm{(}x\mathrm{)}\right)$  in the top or bottom as a part of your limit equation. You may need to factor your equation (think difference of two squares) to see the $1–\mathit{cos}\left(\mathrm{(}x\mathrm{)}\right)$ piece.