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For a non-zero complex number $z$, let $\arg ( z )$ denote the principal argument with $-\pi<\arg ( z ) \leq \pi$. Then, which of the following statement (s) is (are) $FALSE$ ?
$(A)$ $\arg (-1- i )=\frac{\pi}{4}$, where $i =\sqrt{-1}$
$(B)$ The function $f: R \rightarrow(-\pi, \pi]$, defined by $f(t)=\arg (-1+i t)$ for all $t \in R$, is continuous at all points of $R$, where $i=\sqrt{-1}$
$(C)$ For any two non-zero complex numbers $z_1$ and $z_2$, $\arg \left(\left(\frac{z_1}{z_2}\right)-\arg \left(z_1\right)+\arg \left(z_2\right)\right.$ is an integer multiple of $2 \pi$.
$(D)$ For any three given distinct complex numbers, $z_1, z_2$ and $z_3$, the locus of the point $z$ satisfying the condition $\arg \left(\frac{\left( z - z _1\right)\left( z _2- z _3\right)}{\left( z - z _3\right)\left( z _2- z _1\right)}\right)=\pi$, lies on a straight line
$A,B,D$
$A,B,C$
$A,B$
$A,C$
Solution
$(A)$ $\arg (-1-i)=\frac{-3 \pi}{4}$
$(B)$ $f ( t )$ is discontinuous at $t =0$
$(C)$ $\arg \left(\frac{ z _1}{ z _2}\right)=\arg \left( z _1\right)-\arg \left( z _2\right)+2 k \pi$
Hence, it is true.
$(D)$ $\arg \left(\frac{z_1-z}{z_3-z}\right)=\pi-\arg \left(\frac{Z_3-Z_2}{Z_1-Z_2}\right)$ is locus of a point lying on circle.