Chapter 7: Problem 36
Complete the square and give a substitution (not necessarily trigonometric) which could be used to compute the integrals. $$\int \frac{z-1}{\sqrt{2 z-z^{2}}} d z$$
Short Answer
Expert verified
Use the substitution \(u = z - 1\) and further \(u = \sin(v)\) for integration.
Step by step solution
01
Rewrite the quadratic expression
First, recognize the expression under the square root, \(2z - z^2\), as a quadratic expression. Rewrite it in a standard quadratic form: \(-z^2 + 2z\).
02
Factor out the negative sign
Factor out a \(-1\) from \(-z^2 + 2z\) to obtain a positive leading coefficient: \[-(z^2 - 2z)\]
03
Complete the square for the quadratic inside
To complete the square for \(z^2 - 2z\), recall the formula: \((z - rac{b}{2})^2 = z^2 - bz + \frac{b^2}{4}\). Here, \(b\) is 2, so we have:\[z^2 - 2z = (z - 1)^2 - 1\]Thus, the expression becomes:\[-((z - 1)^2 - 1) = -(z - 1)^2 + 1\]
04
Substitute to simplify the integral
Substitute \(u = z - 1\), which implies \(dz = du\) and changes the expression under the square root:\[\int \frac{z-1}{ ext{sqrt}(1 - u^2)} \, du\]This simplification gives us the integral:\[\int \frac{u}{ ext{sqrt}(1 - u^2)} \, du\]
05
Introduce another substitution
Recognize that the expression under the new integral corresponds to a form involving \(1 - u^2\), suggesting a trigonometric substitution for simplicity in integration:Let \(u = \sin(v)\), then \(du = \cos(v) \, dv\) and our integral becomes:\[\int \frac{\sin(v)}{\cos(v)} \cdot \cos(v) \, dv = \int \sin(v) \, dv\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Completing the Square
When it comes to simplifying quadratic expressions, completing the square is a powerful technique. This method helps rewrite a quadratic in a more manageable form.
In our exercise, the quadratic expression is given as oindent \( -z^2 + 2z \). To complete the square, we first focus on the expression inside the parentheses: \( z^2 - 2z \).
By adding and subtracting the square of half the coefficient of \( z \), we reshape it as \((z - 1)^2 - 1 \).
In our exercise, the quadratic expression is given as oindent \( -z^2 + 2z \). To complete the square, we first focus on the expression inside the parentheses: \( z^2 - 2z \).
By adding and subtracting the square of half the coefficient of \( z \), we reshape it as \((z - 1)^2 - 1 \).
- Start by identifying the linear coefficient, which is \( b = 2 \).
- Divide \( b \) by 2 to get \( 1 \), and square it to find \( 1^2 = 1 \).
- Add and subtract this square inside the expression to complete the square.
Trigonometric Substitution
Trigonometric substitution is a tactical maneuver used to simplify integrals involving square roots. This technique turns tricky algebraic expressions into simpler trigonometric forms. Consider the integral in the exercise, \( \int \frac{u}{\sqrt{1 - u^2}} \, du \).
If the expression under the square root features a form like \( 1 - u^2 \), trigonometric functions such as sine and cosine are ideal for substitution.
If the expression under the square root features a form like \( 1 - u^2 \), trigonometric functions such as sine and cosine are ideal for substitution.
- In our problem, substitute \( u = \sin(v) \), resulting in \( du = \cos(v) \, dv \).
- The integral now transforms into a simpler trigonometric integral: \( \int \sin(v) \, dv \).
Substitution Method
The substitution method is like a math-friendly translation tool. It simplifies integrals by changing variables, helping you tackle complex problems more easily.In our exercise, we first used substitution by setting \( u = z - 1 \). This makes the variable change straightforward since \( du = dz \).
- By expressing \( z \) in terms of \( u \), the original integral becomes more manageable.
- The goal is to replace expressions within the integral in terms of \( u \), simplifying the expression to an easier form.
Definite Integrals
Definite integrals are a crucial part of calculus, connecting geometry with algebra. They help calculate the area under a curve, providing numerical results that describe real-world situations. Although our exercise focuses on indefinite integrals, understanding definite integrals is important.A definite integral involves integration over a specific interval \([a, b]\). The fundamental theorem of calculus relates this to antiderivatives, offering a neat formula for evaluating these integrals.
- To convert an indefinite integral to a definite one, establish the limits of integration.
- Calculate the antiderivative and evaluate it at these limits.