Line Current in Three Dimensions

[musiliu]

Homework Statement

[PLAIN]http://img515.imageshack.us/img515/5139/physicsproblem.jpg

Homework Equations

in the image

The Attempt at a Solution

I don't know if i placed the angles theta1 and theta2 correctly in the diagram..I feel like this is incorrect, since the value i calculated for magnetic field is negative..and the direction is positive y, so it feels incorrect to me...

can someone do this problem and check if my answer is correct?

 

[musiliu]

i really need help with this problem , i am more confused than ever:

is r perpendicular the distance from the point to the start of the current? in which case, it is sqrt(2)?
or is it the perpendicular distance from the point to the z axis? in which case it is 1...

how come i get a negative magnitude?(in my answer i just made it positive)
does that mean the direction has to be the opposite? so it has to be -y direction?

please i really need help

 

[musiliu]

i am begging for help, the problem is due tomorrow,
the only equation i was given for magnetic field due to line current was the one i used in the image, and i don't think i am expected to solve it by deriving the bio-savart law again..i need help please