## Quick Reference

If *y* = f(*x*) and a function can be found so that *x* = g(*y*), then g(*y*) is said to be the inverse function of f(*x*). If *y* is a trigonometrical function of the angle *x*, say *y* = sin*x*, then *x* is the **inverse trigonometrical function** of *y*, written *x* = arcsin*y* or sin^{−1}*y*. Similarly, the other trigonometrical functions form the inverse trigonometrical functions cos^{−1}*y*, tan^{−1}*y*, cot^{−1}*y*, sec^{−1}*y*, and cosec^{−1}*y*. **Inverse hyperbolic functions** are also formed in this way, e.g. arcsinh*y* or sinh^{−1}*y*, cosh^{−1}*y*, and tanh^{−1}*y*.

*Subjects:*
Mathematics.

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