Chapter 16: Problem 14
Find the equation of the tangent to \(y=\frac{1}{x^{2}}\) where \(x=-1 .\)
Short Answer
Expert verified
Question: Find the equation of the tangent to the curve \(y = \frac{1}{x^2}\) at the point where \(x = -1\).
Answer: The equation of the tangent to the curve at the given point is \(y = 2x + 3\).
Step by step solution
01
Find the Point on the Curve
We are given the \(x\) value as \(x= -1\). We now find the \(y\) value by plugging this into the equation of the curve. This will give us the point \((x,y)\) where the tangent line touches the curve:
$$
y = \frac{1}{x^2} = \frac{1}{(-1)^2} = 1
$$
So, the tangent touches the curve at the point \((-1, 1)\).
02
Differentiate the Equation of the Curve
Differentiate \(y = \frac{1}{x^2}\) with respect to \(x\) to obtain the slope function of the curve:
$$
y' = \frac{d}{dx} \left( \frac{1}{x^2} \right) = -\frac{2}{x^3}
$$
03
Find the Slope of the Tangent at the Given Point
Substitute the given \(x\) value (\(x=-1\)) into the derivative to find the slope of the tangent at the point:
$$
m = y'(-1) = -\frac{2}{(-1)^3} = 2
$$
The slope of the tangent at the point \((-1,1)\) is \(2\).
04
Write the Equation of the Tangent Line
Now we can use the point-slope form of a linear equation (\(y-y_1=m(x-x_1)\)) to write the tangent equation using the point \((-1,1)\) and slope \(2\):
$$
y-1 = 2(x-(-1))
$$
Simplify the equation to obtain the final tangent equation:
$$
y = 2x+3
$$
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Derivatives
In calculus, derivatives signify the rate at which a function changes at any given point. Essentially, when you find the derivative of a function, you are determining how the y-value (output) changes as the x-value (input) changes.
For any function, its derivative is a new function that provides the slope or steepness of the tangent line at any given point along the original function's curve.
For any function, its derivative is a new function that provides the slope or steepness of the tangent line at any given point along the original function's curve.
- For example, the derivative of the function \( y = \frac{1}{x^2} \) is \( y' = -\frac{2}{x^3} \), representing how quickly this function is changing at any value of \( x \).
- This derivative is essential for calculating the slope of the tangent line at any point.
Tangent Line
The tangent line is a straight line that touches a curve at only one point. This line represents the localized linear approximation of the curve at the point of contact.
Tangent lines are crucial as they provide a simple representation of the curve near a tiny section around the point of tangency.
Tangent lines are crucial as they provide a simple representation of the curve near a tiny section around the point of tangency.
- It's identified by a slope equal to the derivative of the function at the given point.
- In our example, the tangent line to the curve \( y = \frac{1}{x^2} \) at \( x = -1 \) touches the curve at only the point \( (-1,1) \).
Differentiation
Differentiation is the process of finding the derivative of a function. It involves applying specific rules to discover a slope function based on the original equation of the curve. This process allows us to determine how a function behaves over time or across different values compared to the initial function.
For a function \( y = \frac{1}{x^2} \), the differentiation of this function results in \( y' = -\frac{2}{x^3} \).
For a function \( y = \frac{1}{x^2} \), the differentiation of this function results in \( y' = -\frac{2}{x^3} \).
- Here, "-" indicates the function decreases as x increases and vice versa.
- The process of differentiation helps us examine changes in functions at exact points, facilitating the sketching of tangent lines.
Point-Slope Form
The point-slope form provides an essential equation to express a line on a graph based on its slope and a particular point it passes through. This approach is especially handy when you're working on finding an equation for a tangent line.
In the point-slope form, the equation is expressed as:
In the point-slope form, the equation is expressed as:
- \( y - y_1 = m(x-x_1) \),
- where \((x_1, y_1)\) is the specific point and \(m\) is the slope.
- \( y - 1 = 2(x + 1) \).