Calculate angles from axis with a 3d vector

[xX1SHOt]

Homework Statement

A vector is given by R(vector) = 1.90 ihat + 1.30 jhat + 2.92 khat.

Find the magnitude of the vector

Find the angle between the vector and the x, y, and z axis

Homework Equations

I have read something about dot product but I am not sure if it applies here

The Attempt at a Solution

R(magnitude)=3.7183867

R(magnitude in xy plane)=2.302

R(magnitude in yz plane)=3.196

R(magnitude in xz plane)=3.484

I don't know if I should have solved for these or if i should try to solve for the angles in each plane specifically. I was just getting numbers to see where it got me.

 

[nicksauce]

Remember that for dot products
$$\vec{u}\cdot\vec{v} = |u||v|\cos{\theta}$$

Where theta is the angle between the vectors. So choose u = your vector R, and v = ihat, and you get the angle between R and the x-axis.

 

[xX1SHOt]

arent v(vector) and v(magnitude the same which follows for u. which means that it would just be cos( 0 ) b/c that is one

 

[diazona]

arent v(vector) and v(magnitude the same which follows for u. which means that it would just be cos( 0 ) b/c that is one

Are you asking if $\vec{v}$ and $|v|$ (to use nicksauce's notation) are the same? They're not... $\vec{v}$ is a vector, while $|v|$ is a scalar. Completely different things. It's like the difference between an arrow and the length of the arrow.

Do you know how to take the dot product of two vectors?

 

[xX1SHOt]

no that's what I am basically asking, we were not taught this but need to know it i guess to do this problem. Also it is not anywhere in the chapter's we are studying

 

[xX1SHOt]

I have to figure this out by tomorrow and i can't really figure out how to do it from looking up up anywhere. Can someone please resolve this one before it is due tomorrow?