Math Problem Statement

Tentukan luas daerah yang diarsir pada gambar lingkaran dengan jari-jari 14 cm dan sudut pusat 90°.

Solution

The problem asks to determine the area of the shaded region in a circle. Given the image:

  • The circle has a radius r=14r = 14 cm.
  • AOB\angle AOB is a right angle, which means it is 9090^\circ.

Steps to solve:

  1. Calculate the area of the sector AOBAOB:

    The area of a sector is given by: Area of sector=θ360×πr2\text{Area of sector} = \frac{\theta}{360^\circ} \times \pi r^2 Here, θ=90\theta = 90^\circ and r=14r = 14 cm. Area of sector=90360×π×142=14×π×196 cm2=49π cm2\text{Area of sector} = \frac{90^\circ}{360^\circ} \times \pi \times 14^2 = \frac{1}{4} \times \pi \times 196 \text{ cm}^2 = 49\pi \text{ cm}^2

  2. Calculate the area of triangle OABOAB:

    Since OAB\triangle OAB is a right triangle with both legs as the radii of the circle: Area of triangle=12×base×height=12×14×14=98 cm2\text{Area of triangle} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 14 \times 14 = 98 \text{ cm}^2

  3. Determine the area of the shaded region:

    The shaded region is the area of the sector minus the area of the triangle: Area of shaded region=49π cm298 cm2\text{Area of shaded region} = 49\pi \text{ cm}^2 - 98 \text{ cm}^2

Approximate Numerical Value:

To give a numerical approximation, use π3.14\pi \approx 3.14: Area of shaded region=49×3.1498=153.86 cm298 cm2=55.86 cm2\text{Area of shaded region} = 49 \times 3.14 - 98 = 153.86 \text{ cm}^2 - 98 \text{ cm}^2 = 55.86 \text{ cm}^2

Final Answer:

The area of the shaded region is approximately 55.86 cm².

Would you like any further details or clarifications?


Related Questions:

  1. How would the result change if the radius were doubled?
  2. What is the general formula for the area of a shaded region for any given central angle θ\theta?
  3. How does the area of the shaded region compare if θ\theta is 180° instead of 90°?
  4. What is the circumference of the circle in this problem?
  5. How would you calculate the perimeter of the shaded region?

Tip: Remember to always check the angle measure and ensure it's correctly applied in sector area calculations.

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Math Problem Analysis

Mathematical Concepts

Geometry
Circle
Area of Sector
Right Triangle

Formulas

Area of sector = (θ / 360) × π × r²
Area of triangle = (1/2) × base × height

Theorems

Sector area formula
Area of right triangle

Suitable Grade Level

Grades 10-12