| Command Summary | Command Syntax | Calculator Compatibility | Token Size |
|---|---|---|---|
| Takes the inverse cosine of a number (usually, an integer or fraction). | cos-1(angle) | This command works on all calculators. | 1 byte |
Menu Location
Press [2nd] COS button to enter cos-1(.
The Arccos (cos^-1) command
The cos<sup>-1</sup>() command returns the inverse cosine of an angle measure. Naturally, the result depends on the angle mode the calculator is in: radian, degree, or (in AMS version 3.10) gradian. You can also use one of the r, °, G marks to specify an angle mode.
For many common angles, cos<sup>-1</sup>() can compute an exact result. Other angles, the calculator will leave alone unless it's in approximate mode (or unless you make it approximate), and then it will give a decimal approximation. As long as the calculator is in radian mode, cos<sup>-1</sup>() can be used with complex numbers as well.
:cos⁻¹(1/2)
π/3
:cos⁻¹(-1/2)
2π/3
:cos(cos⁻¹(x))
x
If cos<sup>-1</sup>() is applied to a list, it will take the inverse cosine of every element in the list.
Advanced Uses
The cos<sup>-1</sup>() of a matrix is not (in general) the same as taking the cosine of every element of the matrix. I hope that someone more qualified to talk about this updates this part of the page.
Error Conditions
- Please update this part too