4th Class Mathematics Geometrical Figures Angle


Category : 4th Class

*   Angle



Inclination between two rays having common end point is called angle.



In the above picture, OP and OR are two rays which have a common end point 0. The inclination between the rays OP and OR is called angle POR and it is denoted as . Point O is called vertex and rays OP and OR are called arms of the angle POR.



* Features of an Angle

  • Angles is measured in degree.
  • Symbol of the degree is "°".
  • Measure of an angle is written as  a° where a is a number. Ex: 45 degree is written as 45°.


* Types of Angles

Angles have been classified into following groups based on their measurement.

  • Acute angle
  • Right angle
  • Obtuse angle



* Acute Angle

An angle which is greater than  0°  and smaller than 90°  is called acute angle




* Right Angle

An angle of exactly 90° is called right angle .




* Obtuse Angle

An angle which is greater than 90° and smaller than 180° is called obtuse angle



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