Question

If sin A = -8/17 with 180 12 years ago

Answer 1

\[\sin(\frac{A}{2})=\pm \sqrt{\frac{1-\cos(A)}{2}}\]
\[\cos(\frac{A}{2})=\pm \sqrt{\frac{1+\cos(A)}{2}}\]
Now we have A is between 180 and 270 which means
A/2 is between 180/2=90 and 270/2=135
So you should be able to determine what signs cos(A/2) and sin(A/2) will be based on that.

Answer 2

Do you need help finding cos(A) given sin(A)=-8/17 with A between 180 and 270?

Answer 3

Yes, please!

Answer 4

A = 208 deg

Answer 5

That is because
\[\sin ^{-1}(-8/17) = 208 \deg\]

Answer 6

What about cos A/2 and tan A/2

Answer 7

Do you have a calculator?

Answer 8

yes

Answer 9

A/2 = 104 deg, so take cos(104) and tan(104)

Answer 10

i get -.95 for cos?

Answer 11

and .33 for tan

Answer 12

Ack! You're using radians, not degrees. Set your calculator to degrees.

Answer 13

and try again.

Answer 14

not even sure how to go from radians to degrees

Answer 15

What kind of calculator are you using?

Answer 16

i have a ti-83

Answer 17

O good.
From the calculator main screen, press mode, then down 4, to angle; it should say RADIAN. You want it to say DEGREE.

Answer 18

now i get cos-.24

Answer 19

Great!

Answer 20

so its -24 degrees? for cos a/2?

Answer 21

nope

Answer 22

didnt think so!

Answer 23

-.24 is a length. It is the x component of a radian propped up to 104 degrees. I'll draw you a picture

Answer 24

you are awesome thanks! have a big midterm tomorrow and stuck on a few problems

Answer 25

Sure, I'm glad to help. I got my math degree from MIT about 10 years ago, so it's nice to see current HS level math problems and help out with answers :-)

Answer 26

this is college!

Answer 27

Oh, srry!

Answer 28

i guess i am still confused on where to plug thijngs in?

Answer 29

Try using your TI to find the value for cos(90), sin(180), and tan(45).
To start, make sure you are in DEGREE mode. Then press cos and 9 and 0 then return.

Answer 30

for cos 90 i get 0

Answer 31

Exact!

Answer 32

sin180 i get o, tan 45 i get 1

Answer 33

exact and exact. Now try sin(104) and tan(104). You've already done a good job getting cos(104), which is -.24

Answer 34

Remember we are plugging in 104 because A = 208 and the problem asks for sin(A/2)

Answer 35

ok

Answer 36

for sin104 i get .97

Answer 37

yes .97 is right

Answer 38

so sin a/2 is .97 degrees? doesnt seem right

Answer 39

Um, .97 is a measurement of the length of the height of a triangle. It's not .97 degrees, it's .97.
sin and cos take angles, and convert them into length measurements.

Answer 40

guess i need to get a tutor

Answer 41

well, I can try to answer as many questions as you have for now. I'm going to be up late anyway.

Answer 42

im trying to solve this one first for sin cos and tan

Answer 43

You have sin and cos already. Now try tan.

Answer 44

i must be missing something bc sin a/2 given the equation above im getting decimals

Answer 45

tan is -4

Answer 46

sin and cos always give answers between -1 and 1.
Just because they are decimals doesn't mean they are in degrees.

Answer 47

The max value of cos(x) for any x is 1
The max value of sin(x) for any x is 1
The min value of cos(x) for any x is -1
and the min value of sin(x) for any x is -1

Answer 48

that i know, but cant seem to find the connect w this problem