Master Polar Coordinates: Solving for Distance Between A and B | Homework Help

[thomas49th]

Homework Statement

Homework Equations

The Attempt at a Solution

a) I can get a quite easily:
theta = + and - pi/3

r = + and - 3a/2

b) Can someone guide me through how to get this. I want to find the distance between A and B
that is

(3a/2,pi/3), (-3a/2,-pi/3)

Thanks :)

 

[thomas49th]

I still don't have a clue how to do part b. The mark scheme mentions using 2rSin(ө), is that the equation for measuring between two poitns? To find the distance do I want a straigh line between A and B or do I want to actually have an arc of length r and angle 2ө? Should I convert to cartesian form using x = rcos(ө) and y = rsin(x)

I don't have a clue :\

Thanks :)