I Wanna Know

[physicsss]

how to do this problem:
Let vector V = 36 i + 24 j - 57 k. What angles does this vector make with the x, y, and z axes?

TY

[Gokul43201]

What do you think ? Any ideas ?

[arildno]

Do you know what the dot product (scalar product) is?

[physicsss]

Yea, I know what they are...but aren't they for when you have 2 vectors?

[arildno]

What makes you think you haven't two vectors at your disposal?

[physicsss]

Can you expand on it more? The problem only gave me one.

[arildno]

Well, does there exist, for example, a vector which is parallell to the x-axis, so that you could use this in calculating angle between the given vector and the x-axis?

[physicsss]

Could you show me an example? (maybe find the angle a 3-d vector (doesnt have to be mine) makes with the x-axis?)

[arildno]

What's "i" in your equation?
What does this symbol stand for?

[physicsss]

i is the x-component, j is the y-com, and k is the z-com.

[ComputerGeek]

Could you show me an example? (maybe find the angle a 3-d vector (doesnt have to be mine) makes with the x-axis?)

how about the X axis?

[arildno]

i is the x-component, j is the y-com, and k is the z-com.
Your vector is:
\vec{V}=36\vec{i}+24\vec{j}-57\vec{k}
\vec{i} is a unit vector PARALLELL to the x-axis, the number multiplied with it is the vector's component along the x-axis (that is, the vector's x-component).
Another way of saying this, is that:
\vec{V}\cdot\vec{i}=36
Are you now able to calculate the angle?

[physicsss]

I just began learning dot products, and I have never done such an operation like this...

[TenaliRaman]

physicssss,
i denotes a unit "vector" along x-axis
j denotes a unit "vector" along y-axis
k denotes a unit "vector" along z-axis

if u find angle of x with i , then with j and then with k ....
what will u have eventually?

-- AI

[physicsss]

what is x in this case? I'm really confused...

[arildno]

physicsssssss, TenaliRaman blundered, his sentence should read:
"if u find angle of V with i , then with j and then with k ....
what will u have eventually?"
Does this clear up?

[physicsss]

not really...is there a formula for finding the angles a vector makes with the axes??

[arildno]

But the i-vector lies along the x-axis!!
So the angle between the vector V and the x-axis must be the same as the angle between i-vector and V