Question

Law of Sines help???

So I have a project and I have to find the measures of angles B and C on all these triangles. They give me measure A and what a and b equal and I know that sinA/a= SinB/b = SinC/c but every time I try and use this it doesn't work out, even when I have an example in my book and I type it into my calculator I get a different answer than the book and I'm just trying to understand what I'm doing wrong. Help would be appreciated!

Answer 1

have you got an example?

Answer 2

Like in the book there is an equation and it says sin 109/RQ=sin39/40
RQ= 40 sin109/sin39
which is about 60.1 cm but when I type it into my calculator I get 33.9

Answer 3

thats equation RQ = is correct

Answer 4

Yeah I know because it's in my book but I keep getting 33.9 and the answer is 60.1???

Answer 5

I type it in just as the equation says.

Answer 6

ok calculators vary in the way you enter data
with mine if in enter 40 * sin109 / sin 39 it gives me 60.09

Answer 7

that is seriously exactly what i type into mine? I don't understand hahah

Answer 8

with some calculators you need to add angle first then sin

Answer 9

try 109 then sine

Answer 10

Okay hold on

Answer 11

It says error

Answer 12

ok the sin 109 is the way to go
try sin 109 then hit exe

Answer 13

I don't see a button that says exe

Answer 14

well whatever button you use to get a result

Answer 15

Okay I get .8167

Answer 16

or does it give you the answer automatically

Answer 17

well it should be 0.9455

Answer 18

is your calculator set to degrees or radians?

Answer 19

I have no clue how do I find out???

Answer 20

thats the problem!!!

Answer 21

i just set mine to radians and got 0.816

Answer 22

* 0.8167

Answer 23

omg, how do I change it to degrees?

Answer 24

what make is ur calculator?

Answer 25

its a TI-84

Answer 26

oh i don't know about those . Mines a Casio
- maybe you can find a manual on-line.

Answer 27

Okay, I will do that, you're a life saver I would have never figured that out! haha thank you(:

Answer 28

yw

Answer 29

Okay could you help me with something really quick actually? I just want to make sure I'm doing this right.

my first equation I have angle A= 62 degrees a= 30 and b=32. So if I'm trying to find angle B I set it up like Sin62/30=SinB/32 right??

Answer 30

and then it's 32*Sin62/30 ?

Answer 31

@welshfella

Answer 32

yes

Answer 33

Okay but then I get .9418 as my answer?

Answer 34

By the way - i used to have a TI a long way back - i remember you changed degrees to radians and vise versa using the MODE key

Answer 35

Yeah I found a video on how to do it so i fixed that(:

Answer 36

oh ok
hold on

Answer 37

okie

Answer 38

sin B = 0.9418 yes

Answer 39

Okay so then is angle B .9418 degrees? I don't get what to do next

Answer 40

no thats the sine of the angle
you need the inverse sine on ur calc - its either marked sin-1 or arcsin

Answer 41

Ohh okay, thank you again, I think that's all I needed to know(:

Answer 42

yw