Let a circle C in complex plane pass through the points ${z_1} = 3 + 4i$, ${z_2} = 4 + 3i$ and ${z_3} = 5i$. If $z( \ne {z_1})$ is a point on C such that the line through z and z1 is perpendicular to the line through z2 and z3, then $arg(z)$ is equal to :
Solution
<p>${z_1} = 3 + 4i$, ${z_2} = 4 + 3i$ and ${z_3} = 5i$</p>
<p>Clearly, $C \equiv {x^2} + {y^2} = 25$</p>
<p>Let $z(x,y)$</p>
<p>$$ \Rightarrow \left( {{{y - 4} \over {x - 3}}} \right)\left( {{2 \over { - 4}}} \right) = - 1$$</p>
<p>$\Rightarrow y = 2x - 2 \equiv L$</p>
<p>$\therefore$ z is intersection of C & L</p>
<p>$\Rightarrow z \equiv \left( {{{ - 7} \over 5},{{ - 24} \over 5}} \right)$</p>
<p>$\therefore$ $Arg(z) = - \pi + {\tan ^{ - 1}}\left( {{{24} \over 7}} \right)$</p>
About this question
Subject: Mathematics · Chapter: Complex Numbers and Quadratic Equations · Topic: Complex Numbers and Argand Plane
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