Whlie solving complex number 1pi in polar form.In book they have taken theta =-pi/4 why not 7pi/4 because the point lie in fourth quadrant and the theta is given by 2pi-angle(alpha) or -angle(alpha). Ans) Actually the arg. of the complex no. is tan-^{1}|1|.THerefore alpha=pi/4. its in 4rth quad therefore theta=-alpha=-pi/4