2.1 & 2.2 Calculate the circumference and area of a circle

• Mathematics
• Lower Secondary (Key Stage 3)

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2.1 Calculate the circumference and area of a circle

What are the properties of a circle?

Circle

The parts of a circle are the radius, diameter, circumference, arc, chord, secant, tangent, sector and segment. A round plane figure whose boundary consists of points equidistant from a fixed point.

What is the radius of a circle?

Radius

Radius is always half the length of its diameter. For example, if the diameter is 4 cm, the radius equals 4 cm ÷ 2 = 2 cm.

What do we mean when talking about the circumference of a circle?

Circumference

Circumference of the circle or perimeter of the circle is the measurement of the boundary of the circle.

How do we find the circumference of a circle?

Khan & Miro Board Activities

https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-area-circumference/e/radius_diameter_and_circumference

https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-area-circumference/e/find-the-radius-or-diameter-of-a-circle-from-the-circumference-or-area

https://jamboard.google.com/d/1e9ZGJoMac0Xmx0RSVPiz0gWIMaly8GxbhNsckIVwehc/edit?usp=sharing

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Hard question!
What is a 'segment' of a circle?

1. a straight line that connects two points on the circumference of a circle
2. a straight line that touches the circumference of a circle at only one point
3. the area enclosed by an arc of a circle and a chord
4. a line that intersects a circle at two distinct points

Hard question!
What is a 'tangent' of a circle?

1. the area enclosed by an arc of a circle and a chord
2. a straight line that connects two points on the circumference of a circle.
3. a line that intersects a circle at two distinct points
4. a straight line that touches the circumference of a circle at only one point

Write down 3 things you learned in this lesson.

Have students enter three things they learned in this lesson. With this they can indicate their own learning efficiency of this lesson.

Write down 2 things you want to know more about.

Here, students enter two things they would like to know more about. This not only increases involvement, but also gives them more ownership.

Ask 1 question about something you haven't quite understood yet.

The students indicate here (in question form) with which part of the material they still have difficulty. For the teacher, this not only provides insight into the extent to which the students understand/master the material, but also a good starting point for the next lesson.

Khan & Miro Board Activities

https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-area-circumference/e/radius_diameter_and_circumference

https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-area-circumference/e/find-the-radius-or-diameter-of-a-circle-from-the-circumference-or-area

https://miro.com/welcomeonboard/U1hzTHdXb0pNYWpaRGJCUTVWNThycXBaNndPcFZScjhrcUtWRG0wTWwwQ0hOYXVUNW1mYzFTVU1wT25JMHRCSnwzNDU4NzY0NTUzNjIyODU4ODU4fDI=?share_link_id=64027286934

https://miro.com/welcomeonboard/WndoZGI5VzVQZThOMTBWNlp5S3ZvRVVRRUhqSVhWOERUWkl3VVRlQ0FyejE0VXFndkdSRzJQQk12dnZFY2ZxRHwzNDU4NzY0NTUzNjIyODU4ODU4fDI=?share_link_id=940821823486

2.2 Calculate the area of a circle

What do we mean by 'area' of a circle?

How do we find the area of a circle?

Area

Khan & Miro Board Activities

https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-area-circumference/e/area_of_a_circle

https://miro.com/welcomeonboard/WVV4SEpDZTNzdEtOd3g4WU1VUk9leVVWVHRkMHdUaFJRaFJJOGQ5eGE4dkQyRldiZHhSallmSzYyUWFRUGc4TXwzNDU4NzY0NTUzNjIyODU4ODU4fDI=?share_link_id=227809747940

https://miro.com/welcomeonboard/WVV4SEpDZTNzdEtOd3g4WU1VUk9leVVWVHRkMHdUaFJRaFJJOGQ5eGE4dkQyRldiZHhSallmSzYyUWFRUGc4TXwzNDU4NzY0NTUzNjIyODU4ODU4fDI=?share_link_id=227809747940

What is the radius of a circle?

What is the diameter of a circle?

What is the circumference of a circle?

How do we find the area of a circle?

Hard question!
What is a 'segment' of a circle?

1. a straight line that connects two points on the circumference of a circle
2. a straight line that touches the circumference of a circle at only one point
3. the area enclosed by an arc of a circle and a chord
4. a line that intersects a circle at two distinct points

Hard question!
What is a 'tangent' of a circle?

1. the area enclosed by an arc of a circle and a chord
2. a straight line that connects two points on the circumference of a circle.
3. a line that intersects a circle at two distinct points
4. a straight line that touches the circumference of a circle at only one point

Write down 3 things you learned in this lesson.

Have students enter three things they learned in this lesson. With this they can indicate their own learning efficiency of this lesson.

Write down 2 things you want to know more about.

Here, students enter two things they would like to know more about. This not only increases involvement, but also gives them more ownership.

Ask 1 question about something you haven't quite understood yet.

The students indicate here (in question form) with which part of the material they still have difficulty. For the teacher, this not only provides insight into the extent to which the students understand/master the material, but also a good starting point for the next lesson.