Electricity rearranging problem

[maccaman]

We have this complex reasoning question (at school) with this weird situation, anyway they say incorporating every part gives the formula
$$V = mgR tan (\theta) / B^2 L^2 cos (\theta)$$

Where V is the velocity
m is the mass
g is the acceleration (gravity)
B is the magnetic field strength
R is the resistance
L is the length

Now this question is a proof and i must prove it using known physics formula's (mainly from electricity).

The closest i got was to proving it was
$$V = mgr / B^2 L^2 sin^2(\theta)$$

If anyone could help me would be greatly appreciated.

 

[Nenad]

try using trigonometric identities

 

[robphy]

I would think that the physical "reasoning" (however complex) would tell you what "formulas" to use. If you post the "reasoning", I'm sure that the proof will present itself.