Functions Inverse Trigonometric Functions Also cotθ=cosec12 θ− =−x12 CHECK YOUR PROGRESS 18.1 1. Find the principal value of each of the following: (a) 1 3 cos 2 − (b) cosec2−1(−) (c) sin 1 3 2 − − (d) tan3−1(−) (e) cot1−1( ) 2. Evaluate each of the following: (a) 1 1 coscos 3 − (b) cosec1 cosec 4.
.In, trigonometric identities are equalities that involve and are true for every value of the occurring where both sides of the equality are defined. Geometrically, these are involving certain functions of one or more. They are distinct from, which are identities potentially involving angles but also involving side lengths or other lengths of a.These identities are useful whenever expressions involving trigonometric functions need to be simplified. An important application is the of non-trigonometric functions: a common technique involves first using the, and then simplifying the resulting integral with a trigonometric identity.