$(a)\;\sqrt{2}\;[cos (\large\frac{\pi}{2})+i \;sin(\large\frac{\pi}{2})]\qquad(b)\;\sqrt{2}\;[cos (-\large\frac{3\pi}{4})+i \;sin(-\large\frac{3\pi}{4})]\qquad(c)\;\sqrt{2}\;[cos (-\large\frac{\pi}{2})+i \;sin(-\large\frac{\pi}{2})]\qquad(d)\;\sqrt{2}\;[cos (\large\frac{3\pi}{2})+i \;sin(\large\frac{3\pi}{2})]$
