Chapter 20: Problem 63
\(\mathrm{PN}\) is the ordinate of any point \(P\) on the hyperbola \(\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1\) and \(A A^{\prime}\) is its transverse axis. If \(Q\) divides \(A P\) in the ratio \(a^{2}: b^{2}\), then \(N Q\) is (A) \(\perp\) to \(A^{\prime} P\) (B) parallel to \(A^{\prime} P\) (C) \(\perp\) to \(O P\) (D) none of these
Short Answer
Step by step solution
Understand the Problem
Analyze Hyperbola Setup
Calculate Coordinates of Q
Determine the Slope of NP and QP
Analyze Relationship Between NQ and AP
Evaluate Perpendicularity of NQ to A'P
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Ordinate of Hyperbola
The ordinate \(PN\), associated with point \(P(x_1, y_1)\), is essentially the distance from \(P\) to the x-axis, where \(N\) lies directly below or above \(P\) along the y-axis. This value \(y_1\) plays a crucial role in defining the exact position of point \(P\) with respect to the center of the hyperbola, also known as the origin \(O(0, 0)\).
- The ordinate \(PN\) is visualized as a line parallel to the transverse axis intersecting \(P\).
- In hyperbola graphing, the ordinate is key to plotting points that reflect the shape and orientation of the hyperbola.
Transverse Axis of Hyperbola
In our given equation \( \frac{x^2}{a^2} - \frac{y^2}{b^2} = 1 \), the transverse axis aligns with the x-axis. The endpoints are the vertices of the hyperbola at points \(A(-a, 0)\) and \(A'(a, 0)\). Thus, the length of the transverse axis is \(2a\).
- The transverse axis helps determine the direction in which the hyperbola opens. Here, it opens horizontally along the x-direction.
- Such an axis is essential when considering the properties of the hyperbola, such as its vertices, foci, and later, its asymptotes.
- In sketching or solving problems, recognizing the transverse axis provides insight into the hyperbola's orientation and structure.
Ratio Division in Geometry
For our problem, if point \(A\) is \((-a, 0)\) and point \(P\) is \((x_1, y_1)\), point \(Q\) divides \(AP\) in this specified ratio. The coordinates of \(Q\) are computed using the section formula as follows:
\[ Q \left( \frac{a^2 x_1 + b^2(-a)}{a^2 + b^2}, \frac{a^2 y_1 + b^2 \cdot 0}{a^2 + b^2} \right) \]
This ratio division is pivotal in various branches of geometry to position a point accurately along a line segment based on desired proportional distances.
- The formula used here effectively weighs the coordinates according to the given ratios to determine the precise division point.
- Understanding the concept of ratio division helps in tackling a variety of geometric constructions and proofs.
- This method is frequently employed in problems involving complex geometric loci and configurations.