Below is a table with the basic formulas for reducing trigonometric functions: sines (sin), cosines (cos), tangents (tg) and cotangents (ctg).
| Angle | Function | sin a | -sin a | cos a | cos a | sin a | -sin a | -cos a | -cos a | -sin a | sin a |
| cos a | cos a | sin a | -sin a | -cos a | -cos a | -sin a | sin a | cos a | cos a | ||
| tg a | -tg a | ctg α | -ctg α | -tg a | tg a | ctg α | -ctg α | -tg a | tg a | ||
| ctg α | -ctg α | tg a | -tg a | -ctg α | ctg α | tg a | -tg a | -ctg α | ctg α |
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