Question

Can somebody help me

Answer 1

`cis(x)=\cos x+i\sin x\\\\cis15^o=\cos15^o+i\sin15^o\\\\\cos15^o=(\sqrt6+\sqrt2)/(4);\ \sin15^o=(\sqrt6-\sqrt2)/(4)\\\\\text{therefore}\\\\7cis15^o=7\left(\cos15^o+i\sin15^o\right)=7\cos15^o+7i\sin15^o\\\\=7\left((\sqrt6+\sqrt2)/(4)\right)+7\left((\sqrt6-\sqrt2)/(4)\right)i`