Question

trig help

Answer 1

well this comes to

cos(theta) = -2/3

so we need to find theta values in the range 0 to 2pi

any ideas?

Answer 2

no :( I don't get it

Answer 3

do I use cos^-1 and pi

Answer 4

the only angles that provide a -ve cosine value will be in the 2nd and 3rd quadrants

so we get theta = cos^-1(-2/3)

try that

Answer 5

131.81?

Answer 6

very good. that's one angle which is in the 2nd quadrant
whats the other angle that will give you a cosine of -2/3?

Answer 7

? I dont know

Answer 8

is that the one when you use 1-pi ?

Answer 9

if you go cos(-131.8) what do you get?

Answer 10

-0.67?

Answer 11

and -0.67 is 2/3! so the other angle is -131.8

have a look at the diagram i've attached

Answer 12

oh !

Answer 13

wow thank you!

Answer 14

as you can see, both angles have the same cosine. one in the 2nd quadrant and the other in the 3rd. this is where the cosine will always be -ve

Answer 15

oh it says its wrong :(

Answer 16

what says its wrong?

Answer 17

my math program

Answer 18

Try 228.2

Answer 19

ok

Answer 20

its wrong aswell

Answer 21

okay

Answer 22

are you in radians or degrees

Answer 23

derees

Answer 24

degrees*

Answer 25

my calculator says its right so i'm not sure what you're doing

cos131.8 = cos (-131.8) = cos 228.2

Answer 26

all equal to -0.6666 or -2/3

Answer 27

oh round to the hundreths

Answer 28

if you dont round off 2/3 youll get 0.6666666666..... recurring

Answer 29

it says the answers are 2.30 and 3.98

Answer 30

Actually 2.30 radians = 131.7802928801 degrees
3.98 radians = 228.0372024621 degrees

Answer 31

so they want it in radians.. -_- sorry guys it didn't specify that..(

Answer 32

thank you!

Answer 33

i asked you before if you were in radians or degrees? and you said degrees
i'll let you off this time

Answer 34

im sorry it didn't specify D:

Answer 35

Well as long as the answer is correct.

Answer 36

dont worry about it