R: Hyperbolic Functions

Hyperbolic {base} | R Documentation

## Hyperbolic Functions

### Description

These functions give the obvious hyperbolic functions. They respectively compute the hyperbolic cosine, sine, tangent, arc-cosine, arc-sine, arc-tangent.

### Usage

    cosh(x)
    sinh(x)
    tanh(x)
    acosh(x)
    asinh(x)
    atanh(x)

### Arguments

`x` | a numeric vector

### See Also

`cos`, `sin`, `tan`, `acos`, `asin`, `atan`.

### Examples

    Ceps <- .Machine$double.eps # ``Computer epsilon''
    x <- seq(-3, 3, len=200)
    stopifnot(
     abs(cosh(x) - (exp(x) + exp(-x))/2) < 20*Ceps,
     abs(sinh(x) - (exp(x) - exp(-x))/2) < 20*Ceps,
     Mod(cosh(x) - cos(1i*x))       < 20*Ceps,
     Mod(sinh(x) - sin(1i*x)/1i)    < 20*Ceps,
     abs(tanh(x)*cosh(x) - sinh(x)) < 20*Ceps
    )

    ## Inverse:
    all(abs(asinh(sinh(x)) - x) < 10*Ceps)
    x[abs(acosh(cosh(x)) - abs(x)) > 100*Ceps] #- imprecise for small x
    all(abs(atanh(tanh(x)) - x) < 100*Ceps)

    all(abs(asinh(x) - log(x + sqrt(x^2 + 1))) < 10*Ceps)
    cx <- cosh(x)
    all(abs(acosh(cx) - log(cx + sqrt(cx^2 - 1))) < 1000*Ceps)

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