Example:Find Angle Measure in Quadrilateral
Explanation:
In Euclidean plane geometry, a quadrilateral is a polygon with four sides (or 'edges') and four vertices or corners. Sometimes, the term quadrangle is used, by analogy with triangle, and sometimes tetragon for consistency with pentagon (5-sided), hexagon (6-sided) and so on. The word quadrilateral is made of the words quad (meaning "four") and lateral (meaning "of sides").
The interior angles of a simple quadrilateral add
up to 360 degrees of arc. (Our solved
example in mathguru.com uses this concept)
Quadrilateral
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Six different types of quadrilaterals
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Edges and Vertices
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4
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http://en.wikipedia.org/wiki/Quadrilateral
Types
of angles
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Here, a and b are supplementary angles.
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Angles equal
to 1/2 turn (180° or two right angles) are called straight angles. (Our solved example in mathguru.com uses this concept)

Right angle
An angle equal to 1/4 turn
(90° or π/2 radians) is called a
right angle. (Our solved example in mathguru.com uses this concept)
Two
lines that form a right angle are said to be perpendicular or orthogonal
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http://en.wikipedia.org/wiki/Angle
The above explanation is copied from
Wikipedia, the free encyclopedia and is remixed as allowed under the Creative
Commons Attribution- ShareAlike 3.0 Unported License.