Question

Please help with Law of Cosine?

Answer 1

I'm literally to the point of tears!!
I CAN NOT GET THIS PROBLEM!! I AM SO FRUSTRATED!!!!
SOMEONE PLEASE HELP ME!!
The teacher provides me with this example:
http://imgur.com/5PI6SiY.jpg

Then has me do this sample problem:
http://imgur.com/rz5c6R8.jpg

Please, I am not looking for solutions, just simple explanations as to how they got 0.2857 on the example because I CAN NOT FIGURE IT OUT!! NO MATTER WHAT I TRY TO DO!!
I am sorry for typing in caps but I am just so sad and so stressed out!
THEY SHOW ME A SOLUTION BUT NOT HOW TO GET IT!! THEY ONLY SAY "SUBSTITUTE."
WHAT THE HECK!? HOW AM I SUPPOSED TO KNOW HOW TO DO SOMETHING WITHOUT AN EXPLANATION!?!
I seriously CAN NOT figure this out!! I am crying right now because I feel so dumb for not being able to figure out this damn problem!!

Please help! :'(

Answer 2

How do they get CosB and CosC!?
What do I need to do?! I tried isolating Cos B / C and dividing a2 + c2  - 2ac by b^2 but none of my calculations match the decimals! :(

Answer 3

i got it!!!!. jus wait ill xplain

Answer 4

@rohith15 thank you so much, please do explain!

Answer 5

So, if I may suggest, it will forever and always make your life easier if you try to draw a picture that matches the question

Answer 6

when they say substitute, it is just the sides. They labelled them a,b,c and b is the side opposite the biggest angle(so it's the biggest side)

Answer 7

that's how they chose where to put everything into the equation, it's just like if I said let x=4, what does x+6=?

Answer 8

@FibonacciChick666 I did draw a picture. It was the first thing I did: http://imgur.com/b3OT90b.jpg
:/

Answer 9

you're doing the second one aren't you?

Answer 10

may i know what is your doubt??

Answer 11

ok so, after you answer rohith, let's walk through the second one

Answer 12

How do we know which angle we have to find there are three angles

Answer 13

It wants each angle

Answer 14

oh

Answer 15

@Rohith15 Thank you so much. You cleared up so many questions. I just didn't know how to isolate CosB. I was trying to divide the rest by b^2, which was clearly dumb of me to do. I just have doubts because my teacher doesn't give me positive feedback and I frankly feel doubtful on my skills. :(

Answer 16

I really get it now . .Let me try and see if I can get the first one. Even just the first step. : )

Answer 17

first learn to be confident of your skills. you cant doubt your own skills. Let pthers say what they want to but dont doubt yourself

Answer 18

*others

Answer 19

Also, no matter what, never say you are bad at math or suck or anything to that effect. Why? If you do, it produces a negative psychological effect that actually makes you bad at said subject