This lesson explains beyond; what is learnt so far about basic geometric figures
and classifying angles according to their measures, about more complex geometric
relationships. You’ll learn many realworld examples of geometric figures and special
angle pairs relationships. The presentation by the instructor will be done in own
handwriting, using video and with the help of several examples with solution. To
easily understand special angle relationships, it is important to recall distinguishing
different types of angles and then enhance skills by learning about the complexity
involved. In this lesson you will learn with the help of video about three
important special angle relationships.
(More text below video...)
(Continued from above)
Here are a few more angle definitions: congruent angles are angles that have the same measure.
E.g. If
ABC and
DEF have the same
measure; you may say that
ABC and
DEF are congruent
angles. It can be represented symbolically,
ABC
DEF.
A bisector of an angle is a ray whose endpoint is the vertex of the angle, and that
divides that angle into two congruent angles. E.g. if BD is the bisector of
ABC, then
ABD
DBC and both of
them have the same measure.
Adding and subtracting angles: if D is a point in the interior of
ABC and
ABC is not a straight
angle, then
ABC is the sum
of two angles,
ABD and
DBC.
Remember: in cases of special angle relationships
• complementary angles are angle pairs, whose sum measures to 90°.
• supplementary angles are angle pairs, whose sum measures to 180° . Line and Angle relationship: When the lines intersect, some special
angle relationships occur. For example: Vertical angles are the opposite angles
formed by intersecting lines and they are.
When the parallel lines are intersected by a transversal, all the acute angles formed
are congruent, and also all the obtuse angles formed are congruent.
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