# 3rd Class Mathematics Points, Lines and Rays Angles

Angles

Category : 3rd Class

### A Right Angle

When a straight line stands upright (perpendicular) on another straight line a right angle is formed. In the given figure, a straight line AB stands upright on the another straight line BC thus the ABC is formed is called a right angle. The line AB stands upright on BC called perpendicular line to BC and represented by AB -L BC. A right angle is represented by a box as shown in the figure. The measurement of a right angle is always (90 degree). In the given figure  Remember the following about a right angle:

• A perpendicular line on another horizontal line forms a right angle.
• The unit for the measurement of an angle is degree (°).
• A right angle is always equal to 90°.
• A square box at the meeting point of two lines represents an angle of90°.
• A perpendicular line between two points is their shortest distance. Which one of the following options represents a right angle?

(a) (b) (c) (d) All of these

(e) None of these

Explanation:  A square box at the vertex represents the right angle. Acute Angle

If the measurement of an angle is less than a right angle or 90° then it is called an acute angle. In the figure given below, is less inclined than the angle shown by a square box of right angle. Hence, is an acute angle.  Obtuse Angle

If the measurement of an angle is more than a right angle or but less than two right angles or then the angle is called an obtuse angle. In the given figure is an obtuse angle. #### Other Topics

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