Chapter 4: Problem 18
Find the measures of the sides of \(\triangle A B C\) and classify each triangle by its sides. $$A(-4,1), B(5,6), C(-3,-7)$$
Short Answer
Expert verified
The triangle is scalene with sides \( \sqrt{106}, \sqrt{233}, \sqrt{65} \).
Step by step solution
01
Calculate Distance AB
To find the length of side AB, use the distance formula: \( AB = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \). For points \( A(-4, 1) \) and \( B(5, 6) \): \[ AB = \sqrt{(5 - (-4))^2 + (6 - 1)^2} = \sqrt{9^2 + 5^2} = \sqrt{81 + 25} = \sqrt{106} \].
02
Calculate Distance BC
Calculate the length of side BC using the distance formula for points \( B(5, 6) \) and \( C(-3, -7) \): \[ BC = \sqrt{(-3 - 5)^2 + (-7 - 6)^2} = \sqrt{(-8)^2 + (-13)^2} = \sqrt{64 + 169} = \sqrt{233} \].
03
Calculate Distance CA
Calculate the length of side CA using the distance formula for points \( C(-3, -7) \) and \( A(-4, 1) \): \[ CA = \sqrt{(-4 - (-3))^2 + (1 - (-7))^2} = \sqrt{(-1)^2 + 8^2} = \sqrt{1 + 64} = \sqrt{65} \].
04
Compare Side Lengths
To classify the triangle by its sides, compare the side lengths: - \(AB = \sqrt{106}\)- \(BC = \sqrt{233}\)- \(CA = \sqrt{65}\).None of the side lengths are equal, so \( \triangle ABC \) is a scalene triangle.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Distance Formula
The Distance Formula is a crucial mathematical tool for determining the distance between two points on a coordinate plane. It comes from the Pythagorean theorem, which helps find the hypotenuse of a right triangle. In a two-dimensional space, the distance between points \(x_1, y_1\) and \(x_2, y_2\) is calculated using:
\[ d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \]
This formula is derived by considering two points as forming the hypotenuse of a triangle on the Cartesian plane.
When applying the Distance Formula, it's important to:
\[ d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \]
This formula is derived by considering two points as forming the hypotenuse of a triangle on the Cartesian plane.
When applying the Distance Formula, it's important to:
- Correctly substitute the coordinates in place of \(x_1, y_1\) and \(x_2, y_2\).
- Follow the order of subtraction as indicated in the formula.
- Carry out the arithmetic carefully, especially when working with negative numbers, to avoid mistakes.
Coordinates in Geometry
Coordinates are the backbone of geometry on a plane, allowing us to precisely identify points and analyze shapes like triangles. A coordinate system is essentially a grid with an x-axis and a y-axis. Each point is defined by:
In problems like triangle classification, having a clear understanding of how to read and use coordinates is vital. Coordinates enable us to:
- An x-coordinate, which tells you how far to move horizontally from the origin (0,0).
- A y-coordinate, which tells you how far to move vertically from the origin.
In problems like triangle classification, having a clear understanding of how to read and use coordinates is vital. Coordinates enable us to:
- Compute distances between points using the Distance Formula.
- Draw accurate graphical representations of geometric shapes.
- Apply other geometric concepts such as the slope of a line or the midpoint formula.
Types of Triangles
Triangles are three-sided polygons, and they can be classified in two primary ways: by their angles or by the lengths of their sides. Here, we focus on classification by side lengths. In this system, there are three main types:
- Equilateral Triangle: All three sides are of equal length. This uniformity in side length means that all internal angles are also equal, each measuring 60 degrees.
- Isosceles Triangle: Two sides are of equal length, while the third is different. The angles opposite the equal sides are also equal.
- Scalene Triangle: All three sides are of different lengths, which means all the angles are also different.