Question

Find the length of A

Diagram below!

Answer 1

So, what do you think? what have you tried?

Answer 2

I'm a bit confused, we've just dove into law of cosine so it most likely deals with that.

Answer 3

I know it's the largest side

Answer 4

ok, cool so you know two sides, and you have an angle between the two

Answer 5

and we want the opposite side, now, can you tell me the law of cosines? (you are correct that that will be used)

Answer 6

\[ c^2 = a^2 + b&2 − 2abcos(C)\]

Answer 7

alright, good, so now C is the angle between sides a and b, do we fit that criteria?

Answer 8

It'll be uhm

\[C^2=11^2+13^2-2(11)(13)Cos(108Deg)\]

Answer 9

Right? @FibonacciChick666

Answer 10

yeppers

Answer 11

WAIT I DID IT RIGHT?lajaflkalfkjakljs

Answer 12

Yes you did, now remember, that is \(C^\color{red}{2}\)

Answer 13

so what do you have to do to get just c?

Answer 14

Square root

I got: 18.23126

Answer 15

@FibonacciChick666

Answer 16

sounds right

Answer 17

what did you get pre-square root?

Answer 18

I'm getting slightly different

Answer 19

Uhmm let me see

Answer 20

332.37886

Answer 21

ah, rounding

Answer 22

ok here is mine http://www.wolframalpha.com/input/?i=sqrt%2811%5E2%2B13%5E2-2%2811%29%2813%29cos%28108%29%29

Answer 23

you did good! you got it, it's just what happens when you round

Answer 24

Oh wait, now I'm kinda confused.

Did I do something wrong >.<?

Answer 25

Oh, I see!

Answer 26

yea, rounding can cause that little difference

Answer 27

Thank you sooo much! @FibonacciChick666

Answer 28

np, and you got it. Have confidence in yourself. You CAN and DID do it :)