R Trigonometric Function


R trigonometric functions include cos(x), sin(x), tan(x), acos(x), asin(x), atan(x), atan2(y,x). Except atan2(y,x), all functions take radians as argument, not degrees.

Sine(π/2):

>sin(pi/2)
[1] 1

Cosine(π):
>cos(pi)
[1] -1

Tangent(π/4):
>tan(pi/3)
[1] 1.732051

Cotangent(π/3):
>1/tan(pi/3)
[1] 0.5773503

Which value has a cosine = -1?
>acos(-1)
[1] 3.141593

Which value has a tangent = 0.5?
>atan(0.5)
[1] 0.4636476
>tan(0.4636476)
[1] 0.5

atan2() take the y and x values as arguments:
>atan2(1,2)
[1] 0.4636476