3. Three alternating currents are given by i1 = 141 Sin (wt +π/4 )
i2 = 30 Sin (wt+ π/2)
i3 = 20 Sin (wt -π/6)
Into a common conductor. Find graphically or otherwise, the equation of the
resultant current and its r. m.s value

An engine runs on the ideal diesel cycle. the cycle has a compression ratio of 20 and a cutoff ratio of 2. the highest temperature in the cycle is 1200 k. if the heat into the system is 300 kj/kg of working fluid and using variable specific heats determine the work produced per mass of working fluid