Points, Lines, Rays, Angles • Topic 2 of 2

Classify Angles: Right, Acute, Obtuse

Angles are classified by their size (measured in degrees °):

  • Right angle: Exactly 90° — looks like a perfect corner (L shape)
  • Acute angle: Less than 90° — smaller than a right angle (sharp, narrow)
  • Obtuse angle: More than 90° — larger than a right angle (wide, blunt)

A small square symbol in the corner means it is a right angle.

Right (90°)Corner of paperAcute (<90°)Sharp, less than 90°Obtuse (>90°)Wide, more than 90°
Solved Examples
1
Worked Example
What angle is at the corner of a square?
SolutionA right angle (90°). All four corners of a square are right angles.
2
Worked Example
A slightly open book makes a sharp angle. What type is it?
SolutionAcute angle — less than 90°, narrow and sharp.
3
Worked Example
A wide-open door makes a large angle. What type is it?
SolutionObtuse angle — more than 90°, wide and open.

Key Points

  • Right = exactly 90° (square corner). Acute = less than 90° (sharp). Obtuse = more than 90° (wide).
  • Compare to the corner of a piece of paper: that is 90°.
  • Acute is smaller than right; obtuse is bigger than right.
Quick Check — 4 MCQs
Tap an option to check your answer0 / 4
Q1.A right angle is exactly:
Explanation: $90^\circ$.
Q2.An acute angle is:
Explanation: Less than $90^\circ$.
Q3.An obtuse angle is:
Explanation: $90^\circ$ to $180^\circ$.
Q4.A corner of a square is a ___ angle.
Explanation: Right ($90^\circ$).
Practice more MCQs → 📝 Assignment · 35 marks