Trig Identity:

In arithmetic, an "identity" is associate equation that is often true. These may be "trivially" true, like "x = x" or usefully true, like the Pythagorean Theorem's       " a² +  b² = c² " for right triangles. There are a lot of Trig identities, however the subsequent are those you are possibly to check and use..

Defining relations for tangent, cotangent, secant, and cosecant(cosec) in terms of sine and cosine.

The cosine of an angle in this context is the ratio of the length of the side that is adjacent to the angle divided by the length of the hypotenuse.

The tangent of an angle in this context is the ratio of the length of the side that is opposite to the angle divided by the length of the side that is adjacent to the angle.

Trigonometric functions:

The functions trigonometric function, cos and tangent of an angle are typically said because the primary or basic trigonometric functions. Their usual abbreviations are sin(θ), cos(θ) and tan(θ), respectively, wherever θ denotes the angle. The parentheses around the argument of the functions areusually omitted, e.g., sin θ and cos θ, if an interpretation is unambiguously attainable.

And also there are many types of trignometric identities  ie  pythagorean identity ,half angle identities