Chapter 12: Problem 23
Diagonals of a rhombus Show that the diagonals of a rhombus (parallelogram with sides of equal length) are perpendicular.
Short Answer
Expert verified
The diagonals of a rhombus are perpendicular because they intersect at right angles.
Step by step solution
01
Understand Properties of a Rhombus
A rhombus is a type of parallelogram where all four sides are of equal length. Therefore, each side can be labeled as \(s\) for side.
02
Diagonals in Rhombus
The diagonals of a rhombus have special properties: they bisect each other at right angles (90 degrees) and each diagonal bisects the rhombus into two congruent triangles.
03
Define Diagonals
Let's label the diagonals as \(d_1\) and \(d_2\). The diagonals intersect at point \(O\), the center of the rhombus.
04
Use Vector Representation
Represent the sides of the rhombus using vectors. Let \( \vec{AC} \) and \( \vec{BD} \) be the diagonals, and \(OA = OC\), \(OB = OD\). This means \( \vec{OA} = \vec{OC} \) and \( \vec{OB} = \vec{OD} \).
05
Show Perpendicularity
For perpendicularity, the dot product of the diagonals must be zero. Calculate \( \vec{AC} \cdot \vec{BD} = 0 \) since their intersection results in two right triangles \((\angle AOB = 90^\circ)\).
06
Conclusion
Since the dot product results in 0, this confirms that the diagonals of a rhombus are perpendicular to each other. Therefore, they divide the rhombus into four right-angled triangles.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Diagonals of a Rhombus
A rhombus is a special type of parallelogram where all sides are of equal length, making it a unique shape with interesting properties. One of these properties is related to its diagonals. Unlike the diagonals of regular parallelograms, which are not necessarily equal or perpendicular, the diagonals of a rhombus are known to bisect each other at right angles. This means each diagonal divides the rhombus into two congruent triangles, highlighting its symmetry.
- Each diagonal splits the rhombus into two equal (congruent) triangles.
- The diagonals intersect at a single point, which acts as the center of symmetry.
- The property of being perpendicular ensures that the angle formed where they intersect is 90 degrees.
Vector Representation in Geometry
Vectors provide a powerful way to represent geometric shapes mathematically, and the rhombus is no exception. In a rhombus, vectors can represent both the sides and the diagonals, allowing a precise study of their characteristics. When we think of diagonals in terms of vectors, using them provides a clear understanding of direction and magnitude.
- Vectors can describe the diagonals of a rhombus by calculating differences between vertex points.
- This representation helps in visualizing how the diagonals bisect each other within a coordinate plane.
- Using vectors keeps the analysis algebraic, allowing calculations such as the dot product to ascertain perpendicularity.
Dot Product and Perpendicularity
The dot product is a fundamental operation in vector algebra, providing insight into the relationship between two vectors. In the context of a rhombus, it helps confirm the perpendicularity of diagonals. For two vectors to be perpendicular, their dot product must equal zero.
- When two vectors are perpendicular, they form a 90-degree angle, which is key for confirming properties in shapes like the rhombus.
- The formula for the dot product of two vectors \(\vec{a}\) and \(\vec{b}\) is given by: \(\vec{a} \cdot \vec{b} = a_xb_x + a_yb_y\), where each vector has components \((a_x, a_y)\) and \((b_x, b_y)\).
- For the diagonals of a rhombus, this translates to solving \(\vec{AC} \cdot \vec{BD} = 0\) to ensure they intersect perpendicularly.