that since they are in perpendicular direction etcetera; so, one can consider the direction and that tau will be i AB and here also from here also I can get that this two are equivalent equal. because I torque equal to il cross b cross b small b. this is force into this that b distance this couple between these two force.
যেহেতু m এবং B পরস্পরের সাথে লম্ব তাই টর্ক হবে iAB।