Radian measure in sin in R?

r trigonometry
Jen Bohold picture Jen Bohold · Jan 28, 2014 · Viewed 11.5k times · Source

I want to calculate the following in R:

sin(52.517°)

and this should be equal to 0.79353. But when I code

sin(52.517)

I get

0.777119

So how can I get the 0.79353. I am not good in math, but I know something is not working with degrees and the radian measure here in R.

Answer

Martin Dinov picture Martin Dinov · Jan 28, 2014

From the help page on sin which you can read by typing in ?sin in the R console:

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

So by default, the trigonometric functions take radians as input and not degrees. To get the sin(52.517) you need to convert those degrees to a radian measure first:

52.517 degrees = 52.517 * (pi/180) = sin(52.517*(pi/180)) = 0.916...

If you do:

sin(52.517*(pi/180))

you get the wanted 0.7935339.

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