The calculator on my computer always solves for the radian of sin and cos. What I need to do is to solve for degrees. I managed to get over this problem with sin but not with cos.

I tried a few experiments by solving for the cos (180 * pi/180) and got the results I was expecting but not with cos (90). I know my calculator probably isn't at fault here so I ask this, is cos(90) define and where else might cos not be defined at? Also is sin ever undefined?

cos(90 degrees) = 0

Sine and cosine are always defined, because their domain is unbounded and there are no discontinuities.
However, because their range is only between -1 and 1 their inverse functions are only defined from -pi to pi.


Additionally, to convert to radians or degrees, you multiply or divide (respectively) the magical constant pi/180.

Sine and cosine are never not undefined

Double negative? :)

(never not) undefined => always undefined

never (not undefined) => never defined

hmmm...

(never not) undefined => always undefined

never (not undefined) => never defined

hmmm...

always undefined and never defined are pretty much the same thing...

(never not) undefined => always undefined

never (not undefined) => never defined

hmmm...

always undefined and never defined are pretty much the same thing...

Which was my point. No matter how you look at it, it's the opposite of what he meant to say. He's fixed it now, so it's a moot point anyway.