Angles are formed when two lines meet.
Acute angles are angles between 0° and 90°.
Obtuse angles are angles between 90° and 180°.
Reflex angles are angles between 180° and 360°.
Complementary angles are two angles that sum up to 90°.
Supplementary angles are two angles which add up to 180°.
Angles which meet at a point .
The sum of angles which meet at a point is equal to 360°.


EXAMPLE
Find the value of the lettered angle in the diagram below.


Solution
a) a + 20° + 100° + 120° = 360°
a + 240° = 360°
a = 360 - 240
a= 120°


b) ( x+10) + ( 4x - 30) + (2x + 30) = 360°
7x + 10° = 360°
7x = 360° - 10°
x = 350/7
x = 50°


EXERCISE 

Find the value of x in the figure below.