ANGLE PROPERTY OF A QUADRILATERAL
A quadrilateral is a polygon with four sides. A quadrilateral has four vertices and two diagonals. For any quadrilateral, the sum of the interior angles is 360°.
a + b + c + d = 360°.
EXAMPLE
Find the size of each lettered angle in the diagram below.
Solution
a) < BCD = a
125° + 85° + 90° + a = 360°
a= 360° - 300°
a= 60°
b) b + 115° = 180°
b = 180° - 115°
b = 65°
Also 105 ° + 120° + b + c = 360°
105° + 120° + 65° + c = 360°
c = 360° - 290°
c= 70°
END OF LESSON EXERCISE
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