# Circle Theorems: Angle in a semicircle is 90 degrees

In this lesson, we will learn that the angle in a semicircle is 90 degrees when the angle is subtended from the diameter. We will prove this result with a general case.

This quiz includes images that don't have any alt text - please contact your teacher who should be able to help you with an audio description.

#### Unit quizzes are being retired in August 2023

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Quiz:

# Intro quiz - Recap from previous lesson

Before we start this lesson, let’s see what you can remember from this topic. Here’s a quick quiz!

Q1.Work out the size of angle x.

1/3

Q2.Work out the size of angle x.

2/3

Q3.Work out the size of angle x.

3/3

This quiz includes images that don't have any alt text - please contact your teacher who should be able to help you with an audio description.

#### Unit quizzes are being retired in August 2023

Why we're removing unit quizzes from the website >
Quiz:

# Intro quiz - Recap from previous lesson

Before we start this lesson, let’s see what you can remember from this topic. Here’s a quick quiz!

Q1.Work out the size of angle x.

1/3

Q2.Work out the size of angle x.

2/3

Q3.Work out the size of angle x.

3/3

# Video

Click on the play button to start the video. If your teacher asks you to pause the video and look at the worksheet you should:

• Click "Close Video"
• Click "Next" to view the activity

Your video will re-appear on the next page, and will stay paused in the right place.

# Worksheet

These slides will take you through some tasks for the lesson. If you need to re-play the video, click the ‘Resume Video’ icon. If you are asked to add answers to the slides, first download or print out the worksheet. Once you have finished all the tasks, click ‘Next’ below.

This quiz includes images that don't have any alt text - please contact your teacher who should be able to help you with an audio description.

#### Unit quizzes are being retired in August 2023

Why we're removing unit quizzes from the website >
Quiz:

# Circle Theorems: Angle in a semicircle is 90º

Don’t worry if you get a question wrong! Forgetting is an important step in learning. We will recap next lesson.

Q1.Work out the size of angle x.

1/3

Q2.Work out the size of angle y.

2/3

Q3.Work out the size of angle x.

3/3

This quiz includes images that don't have any alt text - please contact your teacher who should be able to help you with an audio description.

#### Unit quizzes are being retired in August 2023

Why we're removing unit quizzes from the website >
Quiz:

# Circle Theorems: Angle in a semicircle is 90º

Don’t worry if you get a question wrong! Forgetting is an important step in learning. We will recap next lesson.

Q1.Work out the size of angle x.

1/3

Q2.Work out the size of angle y.

2/3

Q3.Work out the size of angle x.

3/3

# Lesson summary: Circle Theorems: Angle in a semicircle is 90 degrees

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## Time to move!

Did you know that exercise helps your concentration and ability to learn?

For 5 mins...

Move around:
Climb stairs

On the spot:
Dance