Dot product vector question

  • Thread starter rambo5330
  • Start date
  • #1
84
0

Homework Statement


i'm having troubles solving this problem in physics involving dot product rule


Vector B is 5m and 60 degress above the x axis
A has the same magnitude as C and C is has 25 more degrees than A ..
find magnitude of A..
B dot C = 35
B dot A = 30

this all we're given.. as far as i can get it i make it down to two equations
cos([tex]\theta[/tex] + 25) = 7/C and cos([tex]\theta[/tex]) = 6/C
 

Answers and Replies

  • #2
rl.bhat
Homework Helper
4,433
7
The two equations should be

cos(θ-60 + 25) = 7/c...(1)
cos(θ-60) = 6/c ....(2)
divide (1) by (2), you get

[tex]\frac{cos(\theta-60 + 25))}{cos(\theta-60)} = 7/6[/tex]

Let (θ - 60) = x
expand cos(x + 25) and divide it by cos(x)and simplify to find x.
 
  • #3
84
0
excellent thank you,

I thought that was the method but i'm still running into trouble expanding cos(x + 25) and dividing to clear... when i expand i get


cosx / (cos(x))(cos(25)) - (sin(x))(sin(25)) = 6/7

i dont see how dividing that by cos(x) now accomplishes anything?

where am i going wrong?
 
  • #4
84
0
nm its all good i got it figured out thanks !
 

Related Threads on Dot product vector question

Replies
2
Views
20K
Replies
5
Views
4K
  • Last Post
Replies
1
Views
1K
Replies
9
Views
7K
  • Last Post
Replies
8
Views
2K
  • Last Post
Replies
17
Views
2K
  • Last Post
Replies
7
Views
10K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
1
Views
6K
  • Last Post
Replies
24
Views
5K
Top