sin(x) function computes the sine value of numeric value x.

sin(x)

x: Numeric value, array or vector

> sin(pi)
[1] 1.224606e-16
> sin(-pi)
[1] -1.224606e-16
> sin(pi/3)
[1] 0.8660254
> sin(pi/2)
[1] 1

Use vector as the argument:

> sin(c(3.2, 1, 0, 12));
[1] -0.05837414  0.84147098  0.00000000 -0.53657292
> x <- c(1.5 * pi, 2 * pi, pi/4, pi/6)
> sin(x)
[1] -1.000000e+00 -2.449213e-16  7.071068e-01  5.000000e-01

Let's plot the function:

> x <- seq(-2 * pi, 2 * pi, by=0.1)
> plot(x, sin(x), typ="l", col="blue")
> abline(h=0,col="green",lty=6)

It's a little bit strange that sin(pi) = 1.224606e-16 ( ≈ 0 ). However, sinpi(x) is accurate for x values.

> sinpi(1)
[1] 0
> sinpi(0.5)
[1] 1
> sinpi(0)
[1] 0
> sinpi(1/3)
[1] 0.8660254
> sinpi(1/4)
[1] 0.7071068