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Find Sector Area with Radius 8 cm and Central Angle π/4 Radians
Mathematics
Grade 10 of Junior High School
Question Content
If the radius of the circle sector is 8 cm and its central angle $\\frac{\\pi}{4}$ then what its area?
Correct Answer
$8\\pi$ cm²
Detailed Solution Steps
1
Step 1: Recall the formula for the area of a sector in radians: $A = \\frac{1}{2}r^2\\theta$, where $A$ is sector area, $r$ is radius, and $\\theta$ is the central angle in radians.
2
Step 2: Substitute the given values $r=8$ cm and $\\theta=\\frac{\\pi}{4}$ into the formula: $A = \\frac{1}{2} \\times 8^2 \\times \\frac{\\pi}{4}$.
3
Step 3: Calculate the value: $A = \\frac{1}{2} \\times 64 \\times \\frac{\\pi}{4} = 32 \\times \\frac{\\pi}{4} = 8\\pi$ cm².
Knowledge Points Involved
1
Sector Area Formula (Radians)
The formula $A = \\frac{1}{2}r^2\\theta$ calculates the area of a sector of a circle, where $r$ is the radius of the circle and $\\theta$ is the central angle of the sector measured in radians. It is derived from the fact that the area of the sector is a fraction $\\frac{\\theta}{2\\pi}$ of the full circle area $\\pi r^2$, simplifying to the radians-based formula.
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