# Homework Help: Component form

1. Feb 12, 2008

### chocolatelover

1. The problem statement, all variables and given/known data
Find an expression in component form for 12.0 m and 170° (i+j)
2. Relevant equations

Ax=Acostheta
Ay=Asintheta

3. The attempt at a solution

I was thinking about using one of these equations, but I don't know which one to use or if there is another way of doing it. Does it matter which one I use?

Would it be

12.0cos170? but I don't know where the i or the j would go

Could someone please show me how to set this problem up?

Thank you very much

2. Feb 12, 2008

### ranger

Yes, it matters which one you use for a particular component. Why not draw the vector on a graph? To break it up into its components: the x component (i) is the first equation you've written down, the y (j) component is the second one. You can prove this to yourself by using the graph and some trigonometry.

As an additional check, you can go back from i and j to polar notion. The magnitude is essentially what I told you in the other thread i.e. |A|. The angle is tan^-1 (y/x) (thats the inverse tangent)

Last edited: Feb 12, 2008
3. Feb 12, 2008

### mjsd

i is usually the x direction
j is usually the y direction
draw a diagram, and see the projection onto the x and y axes to visualise, then use trig to determine which equation to use.

4. Feb 13, 2008

### chocolatelover

Thank you very much

Does 12sin10 look right for the i (x component)?

Thank you

Last edited: Feb 13, 2008
5. Feb 13, 2008

### chocolatelover

Can someone please tell me if this is correct?

Thank you

6. Feb 13, 2008

### mjsd

one thing is unclear here... is the angle measuring from the positive x-axis?
draw a diagram if unsure what is what.

7. Feb 13, 2008

### chocolatelover

Thank you

Yes. Would i be 12cos10 and would j be 12sin10? Would I use 10°? (180-170)

Thank you

Last edited: Feb 13, 2008
8. Feb 13, 2008

### chocokat

Yes, just be careful. 170° is in the 2nd quadrant, so your 'x' or 'i' value will be negative. So, it's actually -(12cos10).

9. Feb 13, 2008

### chocolatelover

Thank you very much

Regards