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Ch. 5 - Complex Numbers, Polar Coordinates and Parametric Equations
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601Non è quello che usi tu?Cambia libro di testo
Capitolo 5, Problema 9

In Exercises 9–20, find each product and write the result in standard form. −3i(7i − 5)

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Recall that the imaginary unit \(i\) has the property \(i^2 = -1\).
Distribute \(-3i\) across the terms inside the parentheses: \(-3i \times 7i\) and \(-3i \times (-5)\).
Calculate each product separately: \(-3i \times 7i = -21i^2\) and \(-3i \times (-5) = 15i\).
Substitute \(i^2\) with \(-1\) in the expression \(-21i^2\) to get \(-21 \times (-1)\).
Simplify the expression to combine the real and imaginary parts, resulting in a number in the form $a + bi$.

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Imaginary Unit (i)

The imaginary unit 'i' is defined as the square root of -1, with the property that i² = -1. It is fundamental in complex numbers and allows for the extension of the real number system to include solutions to equations like x² + 1 = 0.
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Multiplication of Complex Numbers

Multiplying complex numbers involves using the distributive property (FOIL method) and applying the rule i² = -1. Each term is multiplied carefully, combining like terms and simplifying to express the result in standard form a + bi.
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Multiplying Complex Numbers

Standard Form of a Complex Number

The standard form of a complex number is written as a + bi, where 'a' is the real part and 'b' is the coefficient of the imaginary part. Expressing results in this form clearly separates real and imaginary components for easier interpretation.
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Complex Numbers In Polar Form