For complex number `z=x+iy` we calculate argument `arg(z)=varphi` by using the following formula

`tan varphi=y/x`

**(i) **In this case we have `"Re"(z)=0` so tangent is undefined but we know that can only happen for `arg(z)=pi/2` or `arg(z)=(3pi)/2` and since `"Im"(z)<0` our **argument is** `arg(z)=(3pi)/2`

**(ii)**

`tan varphi=(-sqrt3/2)/(1/2)=-sqrt3`

Hence we have `varphi=(2pi)/3` or `varphi=(5pi)/3` . Since our number `z` is in 4th quadrant **argument is** `arg(z)=(5pi)/3` ` `

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