Question

Given C = 118, B = 50, and c = 15, use the law of sine to solve the triangle for the value of a... would I use the formula a/ sin A = b/ sin B?

Answer 1

sin C/c = sin B/b

Answer 2

A^2=B^2+C^2-2ab cos a

Answer 3

hero I used that formula earlier and I got b = 6.355932203

Answer 4

i know i have to plug this in to a/ sin A = b/ sin B but I keep getting the wrong answer

Answer 5

118 + 50 + A = 180
solve for A

Answer 6

\[\frac{b}{\sin(50)}=\frac{15}{\sin(118)}\]
\[b=\frac{15\sin(50)}{\sin(118)}\]
make sure your calculator is in "degree" mode since you are working with degrees

Answer 7

i get something pretty close to 13
http://www.wolframalpha.com/input/?i=15sin%2850%29%2Fsin%28118%29

Answer 8

I'm used to the sin being on the top, not the bottom. Guess it really doesn't matter

Answer 9

okay I worked it all out and i got a = 3.12?? but I know that's not right..

Answer 10

Did you find angle A?

Answer 11

yes. C is 118 and B is 50. I added those together and subtract it from 180 and it gave me 12

Answer 12

Angle A is so small. I expect its side to be small as well.

Answer 13

yes. so I have a/12 = 13/50...I multiply 12 and 13 and got 156. divide that by 50 i get 3.12..but that's not the right answer

Answer 14

Must be the ambiguous case

Answer 15

my choices are 17.29, 4.76, 4.07, 2.31, 3.53...obviously its not going to be 17.29

Answer 16

so that can be ruled out

Answer 17

this line
so I have a/12 = 13/50
is not correct

Answer 18

what was my mistake?

Answer 19

we found \(b\) right? \(b=13\)

Answer 20

yes and the formula is a/ sin A = b/ sin B

Answer 21

ok so \(\frac{a}{\sin(15)}=\frac{13}{\sin(50)}\) making \(a=\frac{13\sin(50)}{\sin(15)}\)

Answer 22

okay, so im confused as of what to do here. divide?

Answer 23

first of all you are supposed to ignore me because that equation was wrong

Answer 24

\(\frac{a}{\sin(15)}=\frac{13}{\sin(50)}\) so \(a=\frac{13\sin(15)}{\sin(50)}\)

Answer 25

that is better

Answer 26

i got 3.9 now

Answer 27

i get \(4.4\) rounded
http://www.wolframalpha.com/input/?i=13sin%2815%29%2Fsin%2850%29

Answer 28

are you using a calculator? easier to put it in wolfram in one step

Answer 29

yes i am..and neither of the answers we are getting is one of my choices..

Answer 30

what are your choices for \(b\) ?

Answer 31

i only have choices for a since that is what i am looking for. when i solve for b i got 6.38..idk how you are getting 13

Answer 32

ok lets go slow, see if we made any mistakes
you have \(C=118^o, c=15, A=50^o\) is that right?

Answer 33

no B = 50, not A

Answer 34

sat, only 1, A = 12
so u have sin 12, not sin 15

Answer 35

oh ok \(B=50^o\) and so \(A=12^o\)

Answer 36

yes

Answer 37

@hartnn so it is!!!

Answer 38

yes, and now u get an answer which is in choices..

Answer 39

then we know \(\frac{a}{\sin(12)}=\frac{15}{\sin(118)}\) and so
\[a=\frac{15\sin(12)}{\sin(118)}\]

Answer 40

i get \(3.53\)
http://www.wolframalpha.com/input/?i=15sin%2812%29%2Fsin%28118%29

Answer 41

yup, thats it.

Answer 42

I got the same too, finally! thank you!

Answer 43

imagine!

Answer 44

Well, at least the right answer was found