What is meant by a right angle?

• A. An angle of 45 degrees.
• B. An angle of 90 degrees.
• C. An angle of 180 degrees.
• D. An angle of 60 degrees.

Answer: (B)

A right angle is an angle that measures exactly 90 degrees. It represents a perfect perpendicular intersection—think of the corner of a square or the way two lines meet at a right angle. In diagrams this is often shown with a small square at the vertex. Since a full circle is 360 degrees, a right angle is one quarter of a circle (360 ÷ 4 = 90). The other common angle measures you might see are smaller than 90 degrees (like 45 or 60, which are acute) or 180 degrees (a straight angle), which is not a corner. So the defining feature of a right angle is its 90-degree measure.