how do you find arcsec 1? please explain. Thanks! how is the answer 0? i thought it would be 1?

Update:

and also, how do you find arccos(cos (-1)) why is it 1 when i think it should be 0? cos -1 turns to cos 1 which is 1, then arccos 1 is 0 isnt it?

and also, how do you find arccos(cos (-1)) why is it 1 when i think it should be 0? cos -1 turns to cos 1 which is 1, then arccos 1 is 0 isnt it?

### 3 Answers

Assuming you’re limiting the answer to [0, 2pi),

arcsec1 =

arccos(1/1) =

arccos1 =

0

sec-1(x) = cos-1(1/x)

So sec-1(1) = cos-1(1) = 0

UPDATE: Remember that cosx is an even function

So cosx = cos(-x)

So cos (-1) = cos(1)

Now arccos(x) is the principle value whose cosine is x

So cos(-1) = .540302305868 and arccos(.540302305868)=1

Now cos(0)=1 and cos-1(1)=0