Let $z$ be a complex number. Then the angle between vectors $z$ and $-iz$ is

Let $z$ be a complex number such that $|z-6|=5$ and $|z+2-6i|=5$. Then the value of $z^{3}+3z^{2}-15z+141$ is equal to

If $a$ and $b$ are real numbers between $0$ and $1$ such that the points $z_1 = a + i$,$z_2 = 1 + bi$,and $z_3 = 0$ form an equilateral triangle,then

If the locus of $z \in \mathbb{C}$, such that $\operatorname{Re}\left(\frac{z-1}{2 z+i}\right)+\operatorname{Re}\left(\frac{\bar{z}-1}{2 \bar{z}-i}\right)=2$, is a circle of radius $r$ and center $(a, b)$, then $\frac{15 a b}{r^2}$ is equal to :

The maximum value of $|z|$ where $z$ satisfies the condition $\left| z + \frac{2}{z} \right| = 2$ is

The area of the triangle whose vertices are complex numbers $z, iz, z + iz$ in the Argand diagram is