Chapter 4: Problem 23
Compute \(F(c)\) from the given information. $$ F^{\prime}(x)=\cos (x), F(\pi / 2)=-1, c=\pi / 6 $$
Short Answer
Expert verified
\( F(c) = -\frac{3}{2} \) at \( c = \pi/6 \).
Step by step solution
01
Understand the Problem
We need to calculate the value of the function \( F(c) \) where \( c = \pi/6 \), given that the derivative \( F'(x) = \, \cos(x) \) and \( F(\pi/2) = -1 \).
02
Antiderivative of the Derivative
Since \( F'(x) = \cos(x) \), the antiderivative or integral of \( \cos(x) \) is \( F(x) = \sin(x) + C \), where \( C \) is an arbitrary constant of integration.
03
Use the Initial Condition
We know that \( F(\pi/2) = -1 \). Substitute \( \pi/2 \) into the antiderivative: \( F(\pi/2) = \sin(\pi/2) + C = -1 \). Since \( \sin(\pi/2) = 1 \), it follows that:\[ 1 + C = -1 \]Solve for \( C \) to get \( C = -2 \).
04
Write the Specific Antiderivative
Now that we know \( C = -2 \), the specific function is \( F(x) = \sin(x) - 2 \).
05
Evaluate \( F \) at \( c = \pi/6 \)
Substitute \( c = \pi/6 \) into \( F(x) = \sin(x) - 2 \) to find \( F(\pi/6) \):\[ F(\pi/6) = \sin(\pi/6) - 2 \]We know \( \sin(\pi/6) = 1/2 \), so:\[ F(\pi/6) = \frac{1}{2} - 2 = -\frac{3}{2} \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Antiderivative
Understanding the concept of an antiderivative is crucial in calculus. When you have a function like \(F'(x)\), which represents the derivative of \(F(x)\), finding the antiderivative involves determining a function whose derivative would return you to \(F'(x)\). In the exercise, \(F'(x) = \, \cos(x)\), and the goal was to find \(F(x)\).
The antiderivative of \(\cos(x)\) is \(\sin(x)\). Therefore, \(F(x)\) initially becomes \(\sin(x) + C\), where \(C\) is a constant. This constant arises because when you derive \(F(x)\), any constant disappears. Thus, it's important to include this " + C" when integrating, as it's a placeholder for all potential vertical shifts of the graph of \(F(x)\). This provides the general form of the antiderivative.
Overall, taking the antiderivative essentially reverses differentiation. It's a crucial tool in finding the original function from its rate of change.
The antiderivative of \(\cos(x)\) is \(\sin(x)\). Therefore, \(F(x)\) initially becomes \(\sin(x) + C\), where \(C\) is a constant. This constant arises because when you derive \(F(x)\), any constant disappears. Thus, it's important to include this " + C" when integrating, as it's a placeholder for all potential vertical shifts of the graph of \(F(x)\). This provides the general form of the antiderivative.
Overall, taking the antiderivative essentially reverses differentiation. It's a crucial tool in finding the original function from its rate of change.
Initial Condition
The initial condition helps determine the exact form of a function when integrating. While taking an antiderivative gives us a family of functions with a constant \(C\), the initial condition specifies which member of this family we have. Think of it like solving a puzzle with a missing piece.In this exercise, the problem provides the condition \(F(\pi/2) = -1\). By substituting \(\pi/2\) into the generalized antiderivative \(F(x) = \sin(x) + C\) and setting it to \(-1\), we solve:
- \(\sin(\pi/2) + C = -1\)
- Since \(\sin(\pi/2) = 1\), the equation becomes \(1 + C = -1\)
Trigonometric Functions
Trigonometric functions like \(\sin(x)\) and \(\cos(x)\) play a significant role in calculus due to their periodic nature and fundamental connections to angles and cycles. Each trigonometric function has a unique derivative and antiderivative.
In this task, you encountered \(\cos(x)\), which is the derivative of \(\sin(x)\). Recognizing these relationships is key:
In this task, you encountered \(\cos(x)\), which is the derivative of \(\sin(x)\). Recognizing these relationships is key:
- Derivative of \(\sin(x)\) is \(\cos(x)\)
- Antiderivative of \(\cos(x)\) is \(\sin(x) + C\)
Definite Integration
Although not explicitly required in this problem, definite integration is a related concept often accompanying antiderivatives. While finding an antiderivative gives a general solution \(F(x)\), definite integration deals with the specific area under a curve between two points. This connects closely with the idea of calculating an exact difference or integral over a specified interval.For definite integration, if you know \(F(x)\) is the antiderivative of \(f(x)\), then the definite integral from \(a\) to \(b\) is calculated as:
- \(\int_a^b f(x) \, dx = F(b) - F(a)\)