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Lesson Example Discussion Quiz: Class Homework

Lesson

Title: Circles

Grade: 1300-a Lesson: S3-L1

Explanation: Hello Students, time to learn definitions. Let us take turns and read definitions and explain the pictures. Try to remember or memorize the definitions. Pay special attention to the pictures and communicate in your own words.

Lesson:

Definition: Circles

A circle is a closed curve in which all points are equally distant from a fixed point called the center. The fixed distance from the center to any point on the circle is called the radius.
The standard equation of a circle in the Cartesian coordinate system with center (h, k) and radius r is given by: \$("x" - "h")^2 + ("y" - "k")^2 = "r"^2\$, where (h, k) are the coordinates of the center of the circle.

$1$

Explanation: In this image, h and k represent the center of the circle and r represents the radius.

Definition: Area of Sector

A sector of a circle is a portion of the circle enclosed by two radii and an arc between them. The area of a sector can be calculated using the formula: Area of Sector = \$("central Angle"/(360°)) \times π"r"^2\$, where Central Angle is the angle formed by the radii at the center of the circle (measured in degrees), and r is the radius of the circle.

$2$

Explanation: In this image, the radius of 5 units and an arc length of 8 units, the sector of the circle defined by this arc length has an area of 20 square units, as determined by the formula \$"A" = ("s" \times "r")/2\$