Angles and Their Classification
An angle is formed when two lines meet at a point. Think about opening a book or a door - the space between creates an angle! The point where the lines meet is called the vertex, and the lines are called the arms of the angle.
We measure angles in units called degrees. A full circle measures 360 degrees, which we write as 360°.
Angles are all around us! You can find them in the corner of your desk, in the hands of a clock, or in the letter "V".
Types of Angles
There are four main types of angles:
Acute Angle
An acute angle measures less than 90°. It looks like a narrow opening, smaller than the corner of a square.
∠
An acute angle (smaller than a right angle)
Right Angle
A right angle measures exactly 90°. It looks like the corner of a square or a capital letter "L".
⊾
A right angle (exactly 90°)
Obtuse Angle
An obtuse angle measures more than 90° but less than 180°. It's wider than a right angle but not a straight line.
⦦
An obtuse angle (larger than a right angle)
Straight Angle
A straight angle measures exactly 180°. It forms a straight line.
—
A straight angle (exactly 180°)
Interactive Angle Explorer
Explore acute, right, obtuse, and straight angles. Drag the point, use the slider or preset buttons, and optionally show a protractor overlay.
How to use the Interactive Angle Explorer:
- Drag the blue point to change the angle.
- Use the slider or the preset buttons for quick examples.
- Turn on "Show protractor" to see degree marks and compare your measurement.