- Definition
When two straight lines cross, the angles that are directly across from each other are called opposite angles, and they are always the same size.
When two lines cross to form an 'X', if one angle measures 40 degrees, the angle directly opposite it also measures 40 degrees.
How to teach this in 30 seconds
Try this analogy: Opposite angles are like the corners across from each other when two straight roads cross; they form the same angle.
Ask your child: If you draw a big X, which two angles look exactly the same?
Common mix-up: Kids often confuse opposite angles with the ones right next to them. Opposite angles are always across the 'X' from each other, not side-by-side.
Examples
- The angles on opposite corners where two straight streets intersect are equal.
- If you know one of the wide angles in an 'X' is 110 degrees, the opposite angle is also 110 degrees.
opposite angles is a term used in Ontario’s Kindergarten to Grade 8 curriculum.
Where this shows up
The descriptions on this page are SmartStudy’s own original, plain-language writing — not the Ministry’s wording. They are aligned to the Ontario Curriculum, © King’s Printer for Ontario. For the Ministry’s official wording, see the source link below. SmartStudy is an independent service and is not affiliated with, endorsed by, or sponsored by the Government of Ontario or the Ministry of Education. Ontario Curriculum and Resources ↗
