Maths > Inverse Trigonometric Function > 2.0 Inverse Trigonometric function

  Inverse Trigonometric Function
    1.0 Introduction
    2.0 Inverse Trigonometric function
    3.0 Properties

2.1 ${\sin ^{ - 1}}x$:
We denote the inverse of sine function by ${\sin ^{ - 1}}x$ (arc $\sin x$) function.
From our previous discussion, the inverse of a function is possible only when it is one-one and onto i.e., bijective. So, we have to choose a certain set of domain and range to consider ${\sin ^{ - 1}}x$ as a function.
a certain set of domain and range to consider ${\sin ^{ - 1}}x$ as a function.

As we know, the domain of sine function is $R$(all real numbers) and range is $[-1,1]$. If we restrict its domain to $\left[ { - \frac{\pi }{2},\frac{\pi }{2}} \right]$ then it becomes one-one and onto with in range of $[-1,1]$. From the graph of sine function as shown in figure, we can also say that it is one-one and onto not only with in the domain of $\left[ { - \frac{\pi }{2},\frac{\pi }{2}} \right]$ but also in $\left[ { - \frac{{3\pi }}{2}, - \frac{\pi }{2}} \right]$, $\left[ {\frac{\pi }{2},\frac{{3\pi }}{2}} \right]$,... etc and its range is $[-1,1]$.
We conclude that the inverse of sine function exists with in all the above mentioned set of domain and range of $[-1,1]$ out of which domain $\left[ { - \frac{\pi }{2},\frac{\pi }{2}} \right]$ is the principle value set. We can write the inverse of sine function as $$y = {\sin ^{ - 1}}x$$ where domain becomes $[-1,1]$ and range becomes $\left[ { - \frac{\pi }{2},\frac{\pi }{2}} \right]$.
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