arcsin and arccos question

[killasnake]

Hi I can't figure some question about arcsin and arccos

1) arcsin(sin(100 degrees))


2) acrcos(cos(-25 degrees))

3) With this graph I am suppose to tell what it is,

Is it 5*tan(x) ??

 

[soroban]

Hello, killasnake!

If you're concerned with "principal angles" only,
. . a trig function and its arc-function "cancel out".

1) arcsin[sin(100°)] .= .100°

2) arccos[cos(-25°)] .= .-25°

3) With this graph I am suppose to tell what it is,
Is it 5*tan(x) ??

You're thinking along the right path
. . but a "5" in front won't change the period.

I believe it is: .y .= .tan [(π/2)x]

 

[killasnake]

Hello, killasnake!

If you're concerned with "principal angles" only,
. . a trig function and its arc-function "cancel out".

1) arcsin[sin(100°)] .= .100°

2) arccos[cos(-25°)] .= .-25°

Yeah thats what I thought as well. I'm doing my homework online which gives you a correct or wrong answer right away and it says it's wrong.

Here is the exact problems

- arcsin(sin(37°)) = 37° <---- correct
- arcsin(sin(-25°)) = -25° <----- correct
- arcsin(sin(100°)) = 100° <----- wrong

why is that? Do you need any more information?

 

[Gene]

Well, sin(90+x)=sin(90-x) so
sin(90+10)=sin(90-10)= sin(80)
It expects arcsin(sin(q)) to be in 4th or 1st quadrant.
arcsin(100) is also = 80
arcsin(-100) is also = -80

 

[killasnake]

oh... okay thank you

 

[themuddaload]

lol yall are doing stuff that we havent even discussed yet...

 

[stapel]

yall are doing stuff that we havent even discussed yet...

So... why are you posting replies, if you have no help to offer?

Please be considerate of the other students here. Thank you.

Eliz.