Created almost 9 years ago, updated 5 months ago
ID 23791
A− A+
Theorem: For any ( \mathbf{z}, \mathbf{w} \in \mathbb{C}^n) , the conjugate of their sum equals the sum of their conjugates:
[ \overline{\mathbf{z} + \mathbf{w}} = \overline{\mathbf{z}} + \overline{\mathbf{w}}]
Proof: For each component ( j) :
[ \overline{(\mathbf{z} + \mathbf{w})}_j = \overline{z_j + w_j} = \overline{z_j} + \overline{w_j} = (\overline{\mathbf{z}} + \overline{\mathbf{w}})_j]
The second equality uses the fact that conjugation distributes over addition for complex numbers: ( \overline{a + bi + c + di} = \overline{(a+c) + (b+d)i} = (a+c) - (b+d)i = (a - bi) + (c - di) = \overline{a+bi} + \overline{c+di}) .
Example:
( \mathbf{z} = (1+i, 2)) , ( \mathbf{w} = (3, -i))
( \mathbf{z} + \mathbf{w} = (4+i, 2-i)) → ( \overline{\mathbf{z} + \mathbf{w}} = (4-i, 2+i))
( \overline{\mathbf{z}} + \overline{\mathbf{w}} = (1-i, 2) + (3, i) = (4-i, 2+i)) ✓
Related property: Similarly, ( \overline{a \cdot \mathbf{z}} = \overline{a} \cdot \overline{\mathbf{z}}) for scalar multiplication.
**Theorem:** For any \(\mathbf{z}, \mathbf{w} \in \mathbb{C}^n\), the conjugate of their sum equals the sum of their conjugates:
\[\overline{\mathbf{z} + \mathbf{w}} = \overline{\mathbf{z}} + \overline{\mathbf{w}}\]
**Proof:** For each component \(j\):
\[\overline{(\mathbf{z} + \mathbf{w})}_j = \overline{z_j + w_j} = \overline{z_j} + \overline{w_j} = (\overline{\mathbf{z}} + \overline{\mathbf{w}})_j\]
The second equality uses the fact that conjugation distributes over addition for complex numbers: \(\overline{a + bi + c + di} = \overline{(a+c) + (b+d)i} = (a+c) - (b+d)i = (a - bi) + (c - di) = \overline{a+bi} + \overline{c+di}\).
**Example:**
- \(\mathbf{z} = (1+i, 2)\), \(\mathbf{w} = (3, -i)\)
- \(\mathbf{z} + \mathbf{w} = (4+i, 2-i)\) → \(\overline{\mathbf{z} + \mathbf{w}} = (4-i, 2+i)\)
- \(\overline{\mathbf{z}} + \overline{\mathbf{w}} = (1-i, 2) + (3, i) = (4-i, 2+i)\) ✓
**Related property:** Similarly, \(\overline{a \cdot \mathbf{z}} = \overline{a} \cdot \overline{\mathbf{z}}\) for scalar multiplication.Copy