Math Problem Statement

Perhatikan pentagon di bawah ini. Temukan luasnya!

Solution

To solve for the area of the pentagon, we can break down the shape into smaller, manageable geometric shapes—specifically triangles and rectangles. The provided information includes side lengths and angles.

Step-by-Step Solution:

  1. Identify shapes:

    • The pentagon can be divided into a right triangle (bottom-left corner) and two non-right triangles.
  2. Right Triangle Area:

    • The right triangle on the left side has two sides of length 1, so the area is: Arearight triangle=12×1×1=0.5\text{Area}_{\text{right triangle}} = \frac{1}{2} \times 1 \times 1 = 0.5
  3. Upper Triangle Area (Angle = 60°):

    • For the triangle formed by sides of lengths 1 and 1 with a 60° angle between them, we use the formula for the area of a triangle with known sides and included angle: Area=12×a×b×sin(θ)\text{Area} = \frac{1}{2} \times a \times b \times \sin(\theta) where a=1a = 1, b=1b = 1, and θ=60\theta = 60^\circ. Area60 triangle=12×1×1×sin(60)=340.433\text{Area}_{60^\circ \text{ triangle}} = \frac{1}{2} \times 1 \times 1 \times \sin(60^\circ) = \frac{\sqrt{3}}{4} \approx 0.433
  4. Bottom Triangle Area (Angle = 150°):

    • For the triangle with side lengths 1 and 2 and a 150° angle, using the same formula: Area150 triangle=12×1×2×sin(150)=12×1×2×12=0.5\text{Area}_{150^\circ \text{ triangle}} = \frac{1}{2} \times 1 \times 2 \times \sin(150^\circ) = \frac{1}{2} \times 1 \times 2 \times \frac{1}{2} = 0.5
  5. Sum the Areas:

    • Add up the areas of the three parts: Total Area=0.5(right triangle)+0.433(60° triangle)+0.5(150° triangle)=1.433\text{Total Area} = 0.5 (\text{right triangle}) + 0.433 (\text{60° triangle}) + 0.5 (\text{150° triangle}) = 1.433

Thus, the total area of the pentagon is approximately 1.433 square units.


Would you like a more detailed explanation of any step? Here are some related questions:

  1. How do you find the area of a triangle using side lengths and angles?
  2. What is the sine of common angles like 30°, 60°, and 90°?
  3. How do you break complex polygons into simpler shapes for area calculation?
  4. How does the Law of Sines help in solving non-right triangles?
  5. Can we calculate the perimeter of this pentagon with the given sides?

Tip: For complex polygons, divide them into smaller shapes like triangles or rectangles to simplify area calculations.

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Math Problem Analysis

Mathematical Concepts

Geometry
Area Calculation
Trigonometry

Formulas

Area of a right triangle: (1/2) * base * height
Area of a triangle with two sides and an angle: (1/2) * a * b * sin(θ)

Theorems

Law of Sines
Basic Trigonometry

Suitable Grade Level

Grades 9-12