Question

http://prntscr.com/93a8cj the heck??

Answer 1

How did you get -1?

Answer 2

Whoops, forgot cos in QIV is positive ^^:
Well, it says 1 is wrong so I thought I'd gotten the sign wrong

Answer 3

Wait no sin is negative in QIV

Answer 4

..................................................
I messed up lemme check my work

Answer 5

Well A is in the fourth quadrant, so cos(1/2) = pi/3 right

Answer 6

ok so A is in QIV so A/2 would be QIII right

Answer 7

Yes, pi/3

Answer 8

cosA(1/2)=pi/3*

So now just take 2pi-pi/3 = A for fourth quadrant

Answer 9

QIV pi/3 is umm... 300 degrees or 5pi/3

Answer 10

Yeah 300 degrees works so that's your A

Answer 11

A = 300/2 = 5pi/6

Answer 12

A/2 = 150

Answer 13

Yup that works to haha

Answer 14

lol

Answer 15

Now just find \[\sin(5\pi/6)\]

Answer 16

\[\frac{\sqrt{3}}{2}\]

Answer 17

make that negative

Answer 18

I mean we could've totally just taken cosA=1/2 => A = arccos(1/2) and plug that in for sin(A/2) wait would that works I'm talking nonsense

Answer 19

Mhm, try again

Answer 20

lol

Answer 21

Wait what

Answer 22

Try what again D:

Answer 23

It's not sqrt(3)/2

Answer 24

-sqrt? o-o

Answer 25

it's 5pi/6

Answer 26

sin 5pi/6 = -sqrt 3/2?

Answer 27

Remember pi/6 is the reference angle

Answer 28

Yeah

Answer 29

and 5pi/6 is in the second quadrant