Math Problem Statement

Determine the perimeter of the shape below as an exact value (note the shape is outlined by solid lines)

Determine the perimeter of the shape below as an exact value (note the shape is outlined by solid lines)

Solution

The shape consists of several segments:

  1. A straight line of length 4cm4 \, \text{cm}.
  2. A circular arc with radius 2cm2 \, \text{cm} subtended by a 120120^\circ angle.
  3. A straight line of length 3cm3 \, \text{cm}.
  4. A circular arc with radius 3cm3 \, \text{cm} subtended by a 210210^\circ angle.

Step 1: Perimeter of straight lines

The total length of the straight segments is: 4cm+3cm=7cm.4 \, \text{cm} + 3 \, \text{cm} = 7 \, \text{cm}.

Step 2: Perimeter contribution from the arcs

The length of an arc is given by the formula: Arc length=2πr×θ360,\text{Arc length} = 2 \pi r \times \frac{\theta}{360^\circ}, where rr is the radius and θ\theta is the central angle.

Arc 1:

For the first arc with radius 2cm2 \, \text{cm} and angle 120120^\circ: Arc length=2π×2×120360=4π3cm.\text{Arc length} = 2 \pi \times 2 \times \frac{120^\circ}{360^\circ} = \frac{4\pi}{3} \, \text{cm}.

Arc 2:

For the second arc with radius 3cm3 \, \text{cm} and angle 210210^\circ: Arc length=2π×3×210360=7π3cm.\text{Arc length} = 2 \pi \times 3 \times \frac{210^\circ}{360^\circ} = \frac{7\pi}{3} \, \text{cm}.

Step 3: Total perimeter

Adding the straight lines and arc lengths together: Perimeter=7+4π3+7π3=7+11π3cm.\text{Perimeter} = 7 + \frac{4\pi}{3} + \frac{7\pi}{3} = 7 + \frac{11\pi}{3} \, \text{cm}. Thus, the exact value of the perimeter is: 7+11π3cm.7 + \frac{11\pi}{3} \, \text{cm}.

Let me know if you need more details or have any questions!

Here are 5 related questions for you:

  1. How do you calculate the length of a circular arc?
  2. What is the formula for the circumference of a full circle?
  3. How does the angle affect the length of an arc?
  4. Can a sector's area be calculated using a similar formula as the arc length?
  5. How would the perimeter change if the angles were different?

Tip: For circular arcs, always double-check whether the angle is given in degrees or radians before applying the formula!

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Math Problem Analysis

Mathematical Concepts

Geometry
Circular Arcs
Perimeter

Formulas

Arc length = 2πr × (θ/360°)
Perimeter = sum of straight line lengths + sum of arc lengths

Theorems

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Suitable Grade Level

Grades 9-10