Complex Arithmetic/Examples/1 2^-1 (4-3i) + 3 2^-1 (5+2i)
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Example of Complex Arithmetic
- $\dfrac 1 2 \paren {4 - 3 i} + \dfrac 3 2 \paren {5 + 2 i} = \dfrac {19} 2 + \dfrac 3 2 i$
Proof 1
\(\ds \) | \(\) | \(\ds \dfrac 1 2 \paren {4 - 3 i} + \dfrac 3 2 \paren {5 + 2 i}\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds \paren {2 - \dfrac 3 2 i} + \paren {\dfrac {15} 2 + 3 i}\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds \paren {\paren 2 + \dfrac {15} 2} + \paren {-\dfrac 3 2 + 3} i\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds \dfrac {19} 2 + \dfrac 3 2 i\) |
$\blacksquare$
Proof 2
Let the complex numbers $\dfrac 1 2 \paren {4 - 3 i}$ and $\dfrac 3 2 \paren {5 + 2 i}$ be represented by the points $P_1$ and $P_2$ respectively in the complex plane.
Complete the parallelogram with $OP_1$ and $OP_2$ as the adjacent sides.
Using Geometrical Interpretation of Complex Addition, the point $P$ represents the complex number $\dfrac {19} 2 + \dfrac 3 2 i$, which is the sum of $\dfrac 1 2 \paren {4 - 3 i}$ and $\dfrac 3 2 \paren {5 + 2 i}$.
Hence, $\dfrac {19} 2 + \dfrac 3 2 i$ is the sum of $\dfrac 1 2 \paren {4 - 3 i}$ and $\dfrac 3 2 \paren {5 + 2 i}$.
$\blacksquare$