Chapter 1: Problem 48
Evaluate the expression and write the result in the form \(a+b i .\) $$ \frac{1-\sqrt{-1}}{1+\sqrt{-1}} $$
Short Answer
Expert verified
The result is \( 0 - i \).
Step by step solution
01
Recognize Complex Numbers
Identify the complex numbers in the expression: \( 1 - \sqrt{-1} \) and \( 1 + \sqrt{-1} \). Here, \( \sqrt{-1} \) represents the imaginary unit \( i \). Thus, the expression is \( \frac{1 - i}{1 + i} \).
02
Multiply by the Conjugate
To simplify the fraction, multiply the numerator and the denominator by the conjugate of the denominator. The conjugate of \( 1 + i \) is \( 1 - i \). So, multiply both parts by \( 1 - i \):\[ \frac{(1-i)(1-i)}{(1+i)(1-i)} \]
03
Simplify the Denominator
The denominator \((1+i)(1-i)\) is a difference of squares: \[ (1)^2 - (i)^2 = 1 - (-1) = 2 \]
04
Simplify the Numerator
Expand the numerator \((1-i)(1-i)\):\[ 1 - 2i + i^2 \] Recall that \( i^2 = -1 \), so it becomes:\[ 1 - 2i - 1 = -2i \]
05
Write the Simplified Expression
Combine the results:\[ \frac{-2i}{2} = -i \]
06
Express in the form \(a + bi\)
Rewrite the simplified result \(-i\) in the form \( a + bi \), where \( a = 0 \) and \( b = -1 \). Thus, it's equivalent to \( 0 - i \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Conjugate of a Complex Number
In the realm of complex numbers, the conjugate is a key concept that helps simplify complex arithmetic. The conjugate of a complex number switches the sign of the imaginary part, making it very useful in rationalizing denominators in expressions. For any complex number expressed as \(a + bi\), its conjugate is \(a - bi\). This process aids in reducing expressions to simpler forms.
- The conjugate of \(1 + i\) is \(1 - i\).
- Multiplying a complex number by its conjugate results in a real number.
- Used mainly for rationalizing denominators in fractions containing complex numbers.
Difference of Squares
The difference of squares is a powerful algebraic tool often used with polynomials and in simplifying complex numbers. The standard identity is \((a+b)(a-b) = a^2 - b^2\). When dealing with complex numbers, this identity helps in simplifying expressions by converting complex products into simpler real numbers.
- Essentially involves two terms where one is subtracted from the other, squared.
- In complex arithmetic, helps convert expressions with imaginary units into real numbers.
- The expression \((1+i)(1-i)\) is an example of a difference of squares, yielding \(1^2 - (i)^2\).
Imaginary Unit
The imaginary unit, denoted as \(i\), is the cornerstone of complex numbers. It is defined by its property \(i^2 = -1\), which sets the foundation for constructing all other complex numbers. Every complex number consists of a real part and an imaginary part.
- Imaginary numbers are expressed as multiples of \(i\), for example, \(-2i\).
- Adding and subtracting imaginary numbers follows similar rules to real numbers.
- Simplifies polynomial equations that have no real solutions by providing a way to include square roots of negative numbers.