College Algebra Complex Numbers Operations with Complex Numbers
Multiplication Interactive Example 1

If and , find z1 · z2.

z1=x1+iy1
x1 |
y1 |
| z2=x2+iy2
x2 |
y2 |
Solution 1 By the definition,
z1 · z2 | = |
| = |
| Solution 2 By formally manipulating the terms as if they involved only real numbers and by replacing i2 by -1 when it occurs,
z1 · z2 | = |
| = |
| = |
| = |

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