# Transforming arccos into arctan: acos2atan

### 5.23.8 Transforming arccos into arctan: acos2atan

The acos2atan command transforms any acoss in an expression to atans, using the identity

arccos(x) =

π
2

− arctan

⎛
⎜
⎜
⎜
⎜
⎝

x

√

1−x2

⎞
⎟
⎟
⎟
⎟
⎠

- acos2atan takes one argument:
  expr, an expression containing inverse trigonometric functions.
- acos2atan(expr) returns expr with any acoss replaced by the appropriate atans.

#### Example.

Input:

acos2atan(acos(x))

Output:

π
2

−arctan

⎛
⎜
⎜
⎜
⎜
⎝

x

√

1−x2

⎞
⎟
⎟
⎟
⎟
⎠