# math

posted by .

if vectors a+b+c=0 and modulus of the vectors a, b and c are 3 ,5 and 7 respectively. find the angle between the vectors a and b.

• math -

let the angle be Ø
by the cosine law

7^2 = 3^2 + 5^2 -2(3)(5)cosØ
30cosØ = 9+25-49
cosØ = -15/30 = -1/2
Ø = 150°

## Similar Questions

1. ### physics

Can you help me with this one also? I know how to do it with 3 vectors but I can't seem to draw it with 4 vectors. The magnitudes of the four displacement vectors shown in the drawing are A=16.0 m, B=11.0 m, C=12.0 m, and D=26.0 m.
2. ### math

given that vectors(p+2q) and (5p-4q) are orthogonal,if vectors p and q are the unit vectors,find the product of vectors p and q?
3. ### math

given that vectors(p+2q) and (5p-4q) are orthogonal,if vectors p and q are the unit vectors,find the dot product of vectors p and q?
4. ### math

Two vectors have magnitudes of 3 units and 8 units respectively. The resultant of these two vectors has a magnitude of 8 units. What is the angle between these two vectors?
5. ### Physics

2 vectors have same magnitude.The magnitude of the resultant vector of these 2 vectors are same as either of both vectors.What is the angle between 2 vectors?
6. ### Science

2 vectors have same magnitude.The magnitude of the resultant vectors is same as either of both vectors.What is the angle between 2 vectors?
7. ### Math vectors

For which of the following conditions will the cross product of two vectors be zero?
8. ### Math

if vectors a+2b and 5a-4b are perpendicular to each other and a and b are unit vectors. Find the angle between a and b.
9. ### Math

Let a, b, and c be unit vectors, such that a+b+c=0. Show that the angle between any two of these vectors is 120 degrees. I proved this geometrically, but now my teacher wants a proof using vectors, and I don't know what to do.
10. ### Physics

Please help me with this its very hard to visualize the problem. The analytical method of adding vectors expressed in terms of their components may be applied to vectors in three dimensions, for which graphical work is inconvenient. …

More Similar Questions