/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 37 Show that the product of the dis... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Show that the product of the distances from the point \((0, c)\) to the lines \(a x+y=0\) and \(x+b y=0\) is $$\frac{\left|b c^{2}\right|}{\sqrt{a^{2}+a^{2} b^{2}+b^{2}+1}}$$

Short Answer

Expert verified
The product of distances is \(\frac{|b c^2|}{\sqrt{a^2 + a^2 b^2 + b^2 + 1}}\).

Step by step solution

01

Distance from Point to First Line

For the line \(ax + y = 0\), the distance \(d_1\) from a point \((x_0, y_0)\) to a line \(ax + by + c = 0\) is given by \(d = \frac{|ax_0 + by_0 + c|}{\sqrt{a^2 + b^2}}\). Here the point is \((0, c)\) and the line is \(ax + y = 0\), so we calculate:\[d_1 = \frac{|a \cdot 0 + 1 \cdot c|}{\sqrt{a^2 + 1^2}} = \frac{|c|}{\sqrt{a^2 + 1}}.\]
02

Distance from Point to Second Line

For the line \(x + by = 0\), we use the same distance formula for a point \((0, c)\). The line equation becomes \(x + by = 0\), so:\[d_2 = \frac{|1 \cdot 0 + b \cdot c|}{\sqrt{1^2 + b^2}} = \frac{|bc|}{\sqrt{1 + b^2}}.\]
03

Calculate the Product of Distances

Now, we find the product of the distances \(d_1\) and \(d_2\):\[d_1 \times d_2 = \frac{|c|}{\sqrt{a^2 + 1}} \times \frac{|bc|}{\sqrt{1 + b^2}} = \frac{|b c^2|}{\sqrt{(a^2 + 1)(1 + b^2)}}.\]
04

Simplify the Expression

We simplify the denominator expression \( (a^2 + 1)(1 + b^2) \):\[(a^2 + 1)(1 + b^2) = a^2(1 + b^2) + (1 + b^2) = a^2 + a^2 b^2 + 1 + b^2.\]Thus, the denominator becomes \( \sqrt{a^2 + a^2 b^2 + b^2 + 1} \).
05

Write the Final Expression

Plug the simplified expression into the product of distances formula:\[d_1 \times d_2 = \frac{|b c^2|}{\sqrt{a^2 + a^2 b^2 + b^2 + 1}},\]which matches the given expression.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Distance from a Point to a Line
When studying analytic geometry, determining the distance from a point to a line is a fundamental skill. This is important for various applications including determining how close two geometrical objects are. To find this distance, you use the perpendicular distance formula:
  • The line equation is defined as \( ax + by + c = 0 \).
  • For a point \((x_0, y_0)\), the distance \( d \) to the line is given by:\[d = \frac{|ax_0 + by_0 + c|}{\sqrt{a^2 + b^2}}.\]
This formula measures the perpendicular or shortest distance between the point and the line. In our specific problem, the point \((0, c)\) is evaluated against two separate lines, \( ax + y = 0 \) and \( x + by = 0 \). We effectively applied this formula to calculate the individual distances using relevant coefficients from each line equation. This ensures that the concept is consistent and can be extended to other points and lines.
By understanding and applying this formula, you can tackle a wide range of geometry problems that involve distances between points and lines.
Product of Distances
Being able to calculate the product of distances not only sharpens your math skills but also allows for comprehensive understanding in multi-faceted geometry questions.
First, you find the individual distances. For our example:
  • Distance from \((0, c)\) to the line \( ax + y = 0 \) simplifies to \( d_1 = \frac{|c|}{\sqrt{a^2 + 1}} \).
  • Distance from \((0, c)\) to \( x + by = 0 \) becomes \( d_2 = \frac{|bc|}{\sqrt{1 + b^2}} \).
To find the product, multiply these distances:\[d_1 \times d_2 = \frac{|c|}{\sqrt{a^2 + 1}} \times \frac{|bc|}{\sqrt{1 + b^2}} = \frac{|b c^2|}{\sqrt{(a^2 + 1)(1 + b^2)}}.\]This highlights the relationship and dependence between the distances, showcasing an important geometrical property. Understanding this concept helps in more complex scenarios where relationships between distances influence further geometric calculations.
Simplification of Expressions
Mathematical simplification is crucial not just to make expressions easier to understand but also to solve problems efficiently. In our example, we simplified a complex algebraic expression in the denominator:
  • We started with \((a^2 + 1)(1 + b^2)\), which expanded into \(a^2(1 + b^2) + (1 + b^2)\).
  • This yields \( a^2 + a^2b^2 + 1 + b^2\).
  • Finally, the simplified form is \( \sqrt{a^2 + a^2b^2 + b^2 + 1} \).
Simplifying allows us to clearly see underlying relationships that could otherwise be obscured in a more complex form. It also makes the math tractable in solving further problems.
This practice not only aids in efficient problem-solving but also ensures precise mathematical communication and understanding. Mastering simplification techniques is instrumental in enhancing your overall comfort and aptitude with mathematical expressions and equations.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Let \(F\) and \(V\) denote the focus and the vertex, respectively, of the parabola \(x^{2}=4 p y .\) If \(\overline{P Q}\) is a focal chord of the parabola, show that $$P F \cdot F Q=V F \cdot P Q$$

Determine the equation of the hyperbola satisfying the given conditions. Write each answer in the form \(A x^{2}-B y^{2}=\) Cor in the form \(A y^{2}-B x^{2}=C\). Foci (0,±5)\(;\) vertices (0,±3)

In this exercise we graph the hyperbola $$\frac{(y-3)^{2}}{5^{2}}-\frac{(x-4)^{2}}{3^{2}}=1$$ (a) Solve the equation for \(y\) to obtain $$y=3 \pm 5 \sqrt{1+(x-4)^{2 / 9}}$$ (b) In the standard viewing rectangle, graph the two equations that you obtained in part (a). Then, for a better view, adjust the viewing rectangle so that both \(x\) and \(y\) extend from -20 to 20

This exercise outlines the steps required to show that the equation of the tangent to the ellipse \(\left(x^{2} / a^{2}\right)+\left(y^{2} / b^{2}\right)=1\) at the point \(\left(x_{1}, y_{1}\right)\) on the ellipse is \(\left(x_{1} x / a^{2}\right)+\left(y_{1} y / b^{2}\right)=1\) (a) Show that the equation \(\left(x^{2} / a^{2}\right)+\left(y^{2} / b^{2}\right)=1\) is equivalent to $$b^{2} x^{2}+a^{2} y^{2}=a^{2} b^{2}$$(1) Conclude that \(\left(x_{1}, y_{1}\right)\) lies on the ellipse if and only if $$b^{2} x_{1}^{2}+a^{2} y_{1}^{2}=a^{2} b^{2}$$(2) (b) Subtract equation ( \(2)\) from equation (1) to show that $$b^{2}\left(x^{2}-x_{1}^{2}\right)+a^{2}\left(y^{2}-y_{1}^{2}\right)=0$$(3) Equation ( 3 ) is equivalent to equation ( 1 ) provided only that \(\left(x_{1}, y_{1}\right)\) lies on the ellipse. In the following steps, we will find the algebra much simpler if we use equation ( 3 ) to represent the ellipse, rather than the equivalent and perhaps more familiar equation (1). (c) Let the equation of the line tangent to the ellipse at \(\left(x_{1}, y_{1}\right)\) be $$y-y_{1}=m\left(x-x_{1}\right)$$ Explain why the following system of equations must have exactly one solution, namely, \(\left(x_{1}, y_{1}\right);\) $$\left\\{\begin{array}{ll}b^{2}\left(x^{2}-x_{1}^{2}\right)+a^{2}\left(y^{2}-y_{1}^{2}\right)=0 & (4) \\ y-y_{1}=m\left(x-x_{1}\right) & (5)\end{array}\right.$$ (d) Solve equation ( 5 ) for \(y\), and then substitute for \(y\) in equation (4) to obtain \(b^{2}\left(x^{2}-x_{1}^{2}\right)+a^{2} m^{2}\left(x-x_{1}\right)^{2}+2 a^{2} m y_{1}\left(x-x_{1}\right)=0\) (e) Show that equation (6) can be written \(\left(x-x_{1}\right)\left[b^{2}\left(x+x_{1}\right)+a^{2} m^{2}\left(x-x_{1}\right)+2 a^{2} m y_{1}\right]=0\) (f) Equation (7) is a quadratic equation in \(x,\) but as was pointed out earlier, \(x=x_{1}\) must be the only solution. (That is, \(x=x_{1}\) is a double root.) Thus the factor in brackets must equal zero when \(x\) is replaced by \(x_{1}\) Use this observation to show that $$m=-\frac{b^{2} x_{1}}{a^{2} y_{1}}$$ This represents the slope of the line tangent to the ellipse at \(\left(x_{1}, y_{1}\right)\) (g) Using this value for \(m,\) show that equation (5) becomes $$b^{2} x_{1} x+a^{2} y_{1} y=b^{2} x_{1}^{2}+a^{2} y_{1}^{2}$$(8) (h) Now use equation (2) to show that equation (8) can be written $$\frac{x_{1} x}{a^{2}}+\frac{y_{1} y}{b^{2}}=1$$ which is what we set out to show.

Find the equation of the line that is tangent to the hyperbola at the given point. Write your answer in the form \(y=m x+b\). $$16 x^{2}-25 y^{2}=400 ;(10,4 \sqrt{3})$$

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.