Cos-1 ??

[Define_Robert]

How do I do cos-1?


I tried to do Math.acos, but it gave me NaN

im using flash 6 btw

[ozmic66]

Math.acos should work

what numbers did you use?
are you using radians?

[Define_Robert]

Math.acos should work

what numbers did you use?
are you using radians?

What are radians?


I just learned sin cos tan at school, so I wanted to try it with flash

[ozmic66]

Hey,

I'm sure that there's a million explenations on the web for that, but i'll give it a try too

radians are just like degrees in that they are a measure of an angle

degrees are different from radians in that they range from 0 to 360, and radians from 0 to 2*PI
(or 6.28..., but it is conventional to write the measure for radians with the PI symbol instead of multiplying out)
but other than their range, deg's and rad's are completely the same!

saying that an angle is 180 degrees, is like saying that it is PI (3.14..) radians


there's actually a reason that people use radians (other than to be annoying) but i can't really remember it right now - try looking it up

so when i said that flash uses radians (like most c based languages out there) i meant that you need to convert whatever degrees you are using to radians

to do that, you multiply the degree amount by PI/180 (or 0.01745329.... but you can see which one is easier to use)
to convert from radians back to degrees, multiply by 180/PI

you can use the flash constant Math.PI for a pretty percise number

also, going back to your original question, remember that:

when using arcCos (cos-1) you input a number value (like adjacent/hypotonous) and get back a radian value (which you can convert to degrees with the above method)

if you want to figure out the cos() of a cetain angle, you input the angle in radians, and get back a ratio (opp/hyp)

i hope that helps

if you have any questions, do ask

[Define_Robert]

Hmm, I'm confused...

I did not understand it entirely, mainly because it's in english

In my homework everything about sin cos tan is good(it's basic), but in Flash I just can't do it

But why are you using PI ?

[ozmic66]

what exactly do you mean 'i can't do it in flash'?

[Define_Robert]

I made a picture(its a sketch)

http://img383.imageshack.us/img383/6787/cos8sy.jpg

Normal I would use cos-1 on my calculator, but here if I use Math.acos I get 0.722734247813416, but on my calculator I get 41.40962211

[ozmic66]

here's the problem:

flash uses radians, meaning its giving you the angle amount in a number between 0 - 2*PI, so...

to convert from radians to degrees, you need to multiply by 180/PI

so 0.722734247813416 radians * 180/PI should equal 41.40962211 degrees

[Define_Robert]

OK thx a lot!!!!

[Mattachoo]

there's actually a reason that people use radians (other than to be annoying) but i can't really remember it right now - try looking it up

The reason why radians is so important is that thye are real numbers. A radian has a unit of... well... number. A degree has a unit of .... degrees. 2 * 360 degrees... doesn't make sense. 2 * 2(PI) radians does however.

1 degree = PI/180

And yes, cos-1 = Math.acos

[ozmic66]

2 * 360 degrees... doesn't make sense. 2 * 2(PI) radians does however.

...i'm not sure i understand why


radians are actually used because they provide a way to measure the actual length of the arch that a certain angle makes with a particular radius
wikipedia