6.1     INTRODUCTION:

An angle is formed when two rays originate from the same end point.

   If two lines intersect each other then vertically opposite angles are equal.

  An angle which measures

(   a  )   0 to 900          —         acute angle

(   b  )   exactly 900       —         right angle

(   c  )   900 to 1800       —       obtuse angle

(   d  )  exactly 1800       —       straight angle

(   e  )   1800 to 3600     —       reflex angle