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!

- cagliero423

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- welshfella

have you got an example?

- cagliero423

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

- welshfella

thats equation RQ = is correct

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- cagliero423

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

- cagliero423

I type it in just as the equation says.

- welshfella

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

- cagliero423

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

- welshfella

with some calculators you need to add angle first then sin

- welshfella

try 109 then sine

- cagliero423

Okay hold on

- cagliero423

It says error

- welshfella

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

- cagliero423

I don't see a button that says exe

- welshfella

well whatever button you use to get a result

- cagliero423

Okay I get .8167

- welshfella

or does it give you the answer automatically

- welshfella

well it should be 0.9455

- welshfella

is your calculator set to degrees or radians?

- cagliero423

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

- welshfella

thats the problem!!!

- welshfella

i just set mine to radians and got 0.816

- welshfella

* 0.8167

- cagliero423

omg, how do I change it to degrees?

- welshfella

what make is ur calculator?

- cagliero423

its a TI-84

- welshfella

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

- cagliero423

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

- welshfella

yw

- cagliero423

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??

- cagliero423

and then it's 32*Sin62/30 ?

- cagliero423

@welshfella

- welshfella

yes

- cagliero423

Okay but then I get .9418 as my answer?

- welshfella

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

- cagliero423

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

- welshfella

oh ok
hold on

- cagliero423

okie

- welshfella

sin B = 0.9418 yes

- cagliero423

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

- welshfella

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

- cagliero423

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

- welshfella

yw

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