--- title: "Types of angles" description: "Identify acute and obtuse angles; compare and order angles up to two right angles by size" canonical: https://lightmysky.com/learn/mathematics/types-of-angles-mt_h0CVtqI2xo source: https://lightmysky.com/learn/mathematics/types-of-angles-mt_h0CVtqI2xo.md retrieved: 2026-10-19 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Types of angles Identify acute and obtuse angles; compare and order angles up to two right angles by size Subject: Mathematics · Area: Geometry · Ages 8 to 9 Page: https://lightmysky.com/learn/mathematics/types-of-angles-mt_h0CVtqI2xo ## Ready when they can - Classify given angles as acute, right, or obtuse - Order four angles from smallest to largest by visual comparison - Identify all acute and obtuse angles in a given triangle or quadrilateral ## Lesson: Acute and obtuse angles You already know a right angle: the square corner of a book or a piece of paper. A right angle is a quarter turn. An acute angle has a positive opening smaller than a right angle. An obtuse angle is greater than a right angle and less than a half turn. A half turn is straight, so it is not obtuse. A zero opening is not acute. *(drawing: At 1 o'clock the hands make a smaller opening than a right angle. That smaller opening is acute.)* **Example.** Use the smaller opening between the hands. At 6 o'clock both openings are half turns, so both are straight. At 1 o'clock it is less than a right angle: acute. At 3 o'clock it is a right angle. At 5 o'clock it is more than a right angle but less than a half turn: obtuse. Smallest to largest: 1, 3, 5, 6. To classify a shape, inspect each corner one at a time. Compare each corner with the bounds: smaller than a right angle is acute, exactly a right angle is right, and greater than a right angle but less than a half turn is obtuse. Count the corners in each group. Rotating a whole angle does not change its opening. Lengthening the arms along their own directions does not change the opening either. Two angles of the same type can have different sizes. To order them, compare the actual opening, not the arm length. **Recap.** An angle with no opening is not acute. Acute means an opening less than a right angle. Obtuse means more than a right angle but less than a half turn. The size of an angle does not change when its arms get longer. ## Practice 34 questions on this page, each with its working shown. ## Needs first - [Right Angles & Turns](https://lightmysky.com/learn/mathematics/right-angles-and-turns-mt_MFfYcnv6Tv) ## Opens up - [What Is an Angle?](https://lightmysky.com/learn/mathematics/what-is-an-angle-mt_3S10OOGPqu) - [Measuring angles](https://lightmysky.com/learn/mathematics/measuring-angles-mt_4MFUAsbx_6) - [Mathematical Precision](https://lightmysky.com/learn/mathematics/mathematical-precision-mt_mywsN77hGZ) - [Lines, Rays & Angles](https://lightmysky.com/learn/mathematics/lines-rays-and-angles-mt_QysgF57dxh)