Inverse trigonometric functions return the following principal values.
| Inverse function | Degrees | Radians |
|---|---|---|
| \(\cos^{-1}x\), \(-1\le x\le1\) | \(0^\circ\le\theta\le180^\circ\) | \(0\le\theta\le\pi\) |
| \(\sin^{-1}x\), \(-1\le x\le1\) | \(-90^\circ\le\theta\le90^\circ\) | \(-\pi/2\le\theta\le\pi/2\) |
| \(\tan^{-1}x\), \(x\in\mathbb R\) | \(-90^\circ<\theta<90^\circ\) | \(-\pi/2<\theta<\pi/2\) |
A principal value is one angle; an equation may have further solutions in its stated interval.
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