Trig {base} R Documentation

## Trigonometric Functions

### Description

These functions give the obvious trigonometric functions. They respectively compute the cosine, sine, tangent, arc-cosine, arc-sine, arc-tangent, and the two-argument arc-tangent.

### Usage

```cos(x)
sin(x)
tan(x)
acos(x)
asin(x)
atan(x)
atan2(y, x)
```

### Arguments

 `x, y` numeric or complex vector

### Details

The arc-tangent of two arguments `atan2(y,x)` returns the angle between the x-axis and the vector from the origin to (x,y), i.e., for positive arguments `atan2(y,x) == atan(y/x)`.

Angles are in radians, not degrees (i.e., a right angle is π/2).

All except `atan2` are generic functions: methods can be defined for them individually or via the `Math` group generic.

### Complex values

For the inverse trigonometric functions, branch cuts are defined as in Abramowitz and Stegun, figure 4.4, page 79. Continuity on the branch cuts is standard.

For `asin()` and `acos()`, there are two cuts, both along the real axis: (-Inf, 1] and [1, Inf). Functions `asin()` and `acos()` are continuous from above on the interval (-Inf, -1] and continuous from below on [1, Inf).

For `atan()` there are two cuts, both along the pure imaginary axis: (-1i*Inf, -1i] and [1i, 1i*Inf). It is continuous from the left on the interval (-1i*Inf, -1i] and from the right on the interval [1i, 1i*Inf).

### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

Abramowitz, M. and Stegun, I. A. (1972). Handbook of Mathematical Functions, New York: Dover.
Chapter 4. Elementary Transcendental Functions: Logarithmic, Exponential, Circular and Hyperbolic Functions

[Package base version 2.2.1 Index]