In the given elliptical P_V diagram :

the work done is positive the change in internal energy is non-zero the work done = \(-\frac{\pi}{4} (P_2 - P_1)(V_2-V_1)\)   the work done = \(\pi(V_2 - V_1)^2 - \pi(P_2 - P_1)^2\)

the work done = \(-\frac{\pi}{4} (P_2 - P_1)(V_2-V_1)\)

The work done = area of P-V diagram : \(a = \frac{V_1-V_1}{2}, b = \frac{P_2-P_1}{2}\) W = \(\pi (\frac{V_2-V_1}{2}) (\frac{P_2-P_1}{2})\) But the cyclic process is anticlockwise. Thus, the work done is negative.