Need help with vector calculue (i think thats wht it is)

[leonne]

Homework Statement

this is for a physics problem

so formula i need to solve V=1/4$$\pi$$$$\epsilon$$ (Qc/(rc-r $$\bullet$$ v)
the particle Q moves in a circle of radius a at constant speed w circle is in xy plane at t=0 charge is at (a,0)on x axis. find potentail of charge in z axis.

Homework Equations

The Attempt at a Solution

so i never really know how to find the r the vector position to field point R
I always put like r=(z²+r²) or something but don't know how they find it. For here they did
r= z z^- a(coswt x^ +sinwt y^) than they got
r²=z² +a²
than they got to something similar to what i always guess r=(z+a)^1/2
so how would i figure this out? What is this exactly called so i can maybe find some youtube videos
thanks

 

[leonne]

nvm i figured it out didnt have to go threw the r=z Z^... i just make a simple graph