6.3 Angle Sum Property of a Triangle
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No.
2(iv)
Example: Finding Missing Angles in Triangle
Explanation:
Vertical angles
Two
lines intersect to create two pairs of vertical angles. One pair consists of
angles A and B; the second pair consists of angles C and D.
In geometry, a pair of angles is said to be vertical (also opposite and vertically opposite, which is abbreviated as vert. opp. ∠s) if the angles are formed
from two intersecting lines and the angles are not adjacent. They all share a vertex. Such
angles are equal in measure and can be described as congruent. (Our solved example in mathguru.com uses this concept)
http://en.wikipedia.org/wiki/Vertical_angles
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.
(Our solved example in mathguru.com also uses the below concept.
This is our own explanation, it is not taken from Wikipedia.)
The sum of all the angles of a Triangle
is 180(Angle Sum
Property of a Triangle)