Obtuse Angles – Larger Than a Right Angle

An obtuse angle is any angle that measures more than 90° but less than 180° – wider and more “open” than a right angle, but not yet a flat line. The word “obtuse” comes from the Latin obtusus, meaning “blunt” or “dull” – the exact opposite of “acute” (sharp), which makes the two terms a natural, easy-to-remember pair.

Obtuse angles sit directly between right angles and straight angles on the number line of possible angle measures, making them the natural next step after mastering right angles.

Recognising an Obtuse Angle

Real-Life Application

• Reclining chairs: a comfortable recline often forms an obtuse angle at the hinge.
• Open laptop screens: a laptop opened wide beyond 90° forms an obtuse angle.
• Roof designs: gently sloped (low-pitch) roofs often meet at an obtuse angle.

Key Takeaways

Practice: Obtuse Angles