Lesson

Being able to identify an angle can help us in this lesson. Let's try this problem to review.

Select the obtuse angle:

A

B

C

D

Worked Solution

Idea summary

A full revolution is made up of 360 degrees, a single degree is written 1\degree.

Angle type | Angle size |
---|---|

\text{Acute angle} | \text{Larger than } 0 \degree, \text{smaller than } 90\degree. |

\text{Right angle} | 90\degree |

\text{Obtuse angle} | \text{Larger than } 90\degree, \text{smaller than } 180\degree. |

\text{Straight angle} | 180\degree |

\text{Reflex angle} | \text{Larger than } 180\degree, \text{smaller than } 360\degree. |

\text{Full revolution} | 360\degree |

Let's learn more about angles on a straight line.

Find the size of the missing angle.

Worked Solution

Idea summary

Angles on a straight line always add up to 180 degrees.

Investigate with and without digital technologies, angles on a straight line, angles at a point and vertically opposite angles. Use results to find unknown angles.