# Mechanics VectorsWatch

#1
hi every1

this question isn't actually vectors, but it's in the same chapter. It's about understanding bearings and using trig.

I put it in a spoiler..

Spoiler:
Show

This is the question

and here are my workings.

ok, so let me guide you through my workings..

Step 1: I've drawn my diagram (hopefully right )

Step 2: The shortest way back is obviously the yellow line^^

Step 3: I know for a fact that the green angle is 120Â° :>

Step 4: And therefore we can work out the 3rd angle.. (360-120-110)

Step 5: Now, If I'm not mistaken, I can use the cosine rule, right?! Well.. as you can see I got a problem

Isn't that the right way to solve this

anyway, I'm confused right now but I'm sure you'll have a solution 4 thiz ^.^

thx

â‚¬: In the (2nd) picture, it's meant to be XÂ² =
0
7 years ago
#2
(Original post by StylaBoy)
...
Don't know what that's meant to be at the end of the equation in the blue box.

You can use the cosine rule to find x, and then the sine rule to find the angle theta.

What's the problem you're having?
#3
Well, just ignore the last bit in the blue box

my problem is when I apply the cosine rule, I get -16.069.. and then I would have to square root, which I can't do with a negative number..

cheers
0
7 years ago
#4
Your working is right, it must be something to do with the way you are putting it into the calculator
0
7 years ago
#5
Using the cosine rule:

Perhaps you typed it in wrong or are working in radians or something.
0
7 years ago
#6
(Original post by Ben121)
Using the cosine rule:

Yeah I agree with Ben I got the same answer too

OP:
This is how I typed it on my calculator

x= 31.8
0
7 years ago
#7
i got: 31.8 (3 s.f)
0
7 years ago
#8
(Original post by StylaBoy)

my problem is when I apply the cosine rule, I get -16.069.. and then I would have to square root, which I can't do with a negative number..

cheers
If you still have a problem, post your working. A couple of people have provided correct values for x.
#9
Ohhh yes thanks guys!

I know what my mistake was.. I've done 625-600

and then 25 Cos 130

thx again, you're the best
0
7 years ago
#10
(Original post by Sokka)
i got: 32.67084434 = 32.7 (3 s.f)

i mean it's fairly straight forward; here's my working:
the other length was 15 not 16
0
7 years ago
#11
(Original post by anshul95)
the other length was 15 not 16
ye man, I changed it asap x] I always get the lengths wrong for some reason
0
X

new posts
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### University open days

• Cranfield University
Cranfield Forensic MSc Programme Open Day Postgraduate
Thu, 25 Apr '19
• University of the Arts London
Open day: MA Footwear and MA Fashion Artefact Postgraduate
Thu, 25 Apr '19
• Cardiff Metropolitan University
Sat, 27 Apr '19

### Poll

Join the discussion

#### Have you registered to vote?

Yes! (228)
39.31%
No - but I will (40)
6.9%
No - I don't want to (41)
7.07%
No - I can't vote (<18, not in UK, etc) (271)
46.72%

View All
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.