Trigonometric identities
The following equations are the most basic and important trigonometric identities. These equations are true for any angle. From them, countless additional identities can be formed. Basic trigonometric identities:
Pythagorean Identities:
a) sin^{2}A + cos^{2} A = 1 b) 1 + tg^{2} A = sec^{2}A c) 1 + cot^{2} A = csc^{2}A You can use the trigonometric identities given above to find trigonometric ratios if you are given the quadrant an angle lies in and the value of one trigonometric ratio. It will be useful to remember the sign of the trigonometric ratios in each quadrant: If sinθ= and , find cosθ and tanθ.
