Co-ratios refer to the relationships and sign changes of trigonometric functions when the angle is altered by 90°, 180°, 270°, or full rotation (360°). These transformations help simplify complex angle expressions using standard trigonometric identities.
| Angle | sin | cos | tan | cot |
|---|---|---|---|---|
| -α | -sin α | +cos α | -tan α | -cot α |
| 90° - α | +cos α | +sin α | +cot α | +tan α |
| 90° + α | +cos α | -sin α | -cot α | -tan α |
| 180° - α | +sin α | -cos α | -tan α | -cot α |
| 180° + α | -sin α | -cos α | +tan α | +cot α |
| 270° - α | -cos α | -sin α | +cot α | +tan α |
| 270° + α | -cos α | +sin α | -cot α | -tan α |
| 360°k - α | -sin α | +cos α | -tan α | -cot α |
| 360°k + α | +sin α | +cos α | +tan α | +cot α |