Chapter 1: Problem 43
Show that the triangle with vertices \(A(8,5), B(1,-2)\). and \(C(-3,2)\) is a right triangle, and find its area.
Short Answer
Expert verified
The triangle is a right triangle with an area of 28 square units.
Step by step solution
01
Calculate the Length of Each Side
To determine if the triangle is right-angled, we must first calculate the length of each side using the distance formula, which is given by \[AB = \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}\]For \( AB \), substitute \((x_1, y_1) = (8, 5)\) and \((x_2, y_2) = (1, -2)\):\[AB = \sqrt{(1 - 8)^2 + (-2 - 5)^2} = \sqrt{(-7)^2 + (-7)^2} = \sqrt{49 + 49} = \sqrt{98} = 7\sqrt{2}\]Repeat for side \( BC \) with points \((1, -2)\) and \((-3, 2)\):\[BC = \sqrt{(-3 - 1)^2 + (2 + 2)^2} = \sqrt{(-4)^2 + (4)^2} = \sqrt{16 + 16} = \sqrt{32} = 4\sqrt{2}\]Lastly, for \( CA \), use points \((8, 5)\) and \((-3, 2)\):\[CA = \sqrt{(8 + 3)^2 + (5 - 2)^2} = \sqrt{(11)^2 + (3)^2} = \sqrt{121 + 9} = \sqrt{130}\]
02
Check for Right-Angled Triangle Using Pythagoras Theorem
To check if the triangle is a right triangle, ensure that the square of the longest side is equal to the sum of the squares of the other two sides. The lengths found are \( 7\sqrt{2} \), \( 4\sqrt{2} \), and \( \sqrt{130} \). Clearly, \( \sqrt{130} \) is the longest. Now, verify:\[(7\sqrt{2})^2 + (4\sqrt{2})^2 = 130\]Calculating each term:\[(7\sqrt{2})^2 = 49 \times 2 = 98\]\[(4\sqrt{2})^2 = 16 \times 2 = 32\]Adding these gives:\[98 + 32 = 130\]Since the equation holds true, the triangle is a right triangle, with \( CA \) being the hypotenuse.
03
Calculate the Area of the Triangle
The area of a triangle is given by the formula:\[\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}\]For a right triangle, we can use the legs as the base and height. Therefore, the area can be calculated using:\[\text{Area} = \frac{1}{2} \times 7\sqrt{2} \times 4\sqrt{2}\]which simplifies to:\[= \frac{1}{2} \times 28 \times 2 = 28\]Thus, the area of the triangle is 28 square units.
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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 helps us find the length of a line segment between two points in a plane. It's particularly handy in geometry, especially when dealing with right triangles. The formula is derived from the Pythagorean Theorem and is given by: \[d = \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}\]
- Here, \((x_1, y_1)\) and \((x_2, y_2)\) are the coordinates of the two points.
- The difference between the \(x\)-coordinates is squared, as well as the difference between the \(y\)-coordinates.
- The sum of these squares gives us the length of the hypotenuse of a right-angled triangle formed by these differences.
Pythagorean Theorem
The Pythagorean Theorem is a cornerstone in geometry, especially useful for determining if a triangle is right-angled. It states that for a right triangle, the sum of the squares of the two shorter sides (legs) is equal to the square of the longest side (hypotenuse). Mathematically, it is expressed as: \[a^2 + b^2 = c^2\]
- Here, \(a\) and \(b\) are the lengths of the legs.
- \(c\) represents the length of the hypotenuse.
Solving the Right Triangle
We checked if \((7\sqrt{2})^2 + (4\sqrt{2})^2 = 130\), finding that the equation holds true. This confirmed the presence of a right angle in the triangle, with \(CA\) as the hypotenuse. Understanding this theorem is crucial in identifying and confirming right triangles.Triangle Area Calculation
Calculating the area of a triangle requires an understanding of base and height. For right-angled triangles, this process is simplified, as the two shorter sides can be used directly as base and height. The area is calculated using the formula: \[\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}\]
- For the given triangle, \(7\sqrt{2}\) and \(4\sqrt{2}\) serve as base and height.
- By plugging these into the formula: \(\frac{1}{2} \times 7\sqrt{2} \times 4\sqrt{2}\), we simplified it to 28 square units.