From ohm's law \\\\(R=\\dfrac{V}{i}\\\\)also the slope of V-i Graph \\\\(S=\\dfrac{V}{i}\\\\)angle with y axis is given by \\\\(\ an \ heta =\\dfrac{I}{V}\\\\)so \\\\(R=S=\\dfrac{1}{\ an\ heta}=\\cot\ heta\\\\)