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Important TermsImportant Terms
• Ray- Ray is a part of line that has one
endpoint and goes on endlessly in the
other direction.
• Line Segment- A part of line that has
two endpoints is known as line segment.
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• Line- A series of point that go
endlessly in both directions is known as
a line.
• Parallel Lines- Two lines that are equal
distance apart and will never intersect
are known as parallel lines.
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• Angle- The figure formed when two
rays share the same endpoints.
• Vertex- The point at which two rays
join together to form an angle is
known as vertex.
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Types Of AnglesTypes Of Angles
• Obtuse Angle- An angle that
measures more then 90° is known as
obtuse angle.
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• Acute Angle- An angle that measures
less then 90° is known as acute angle.
• Right Angle- An angle that measures
90° is known as right angle.
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• Straight Angle- An angle that
measures 180° is known as straight
angle.
• Reflex Angle- An angle that is
greater then 180° is known as reflex
angle.
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More AnglesMore Angles
Adjacent Angles-Adjacent Angles- Adjacent angles areAdjacent angles are
angles which have a common side and aangles which have a common side and a
common vertex but no interior points incommon vertex but no interior points in
common.common.
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• Vertically Opposite Angles- Vertically
Opposite Angles are the angles opposite
to each other when two lines cross.
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• Corresponding Angles- When two lines
are crossed by another line the angles in
matching corners are called
corresponding angles.
x
y
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• Alternate Interior Angles- When two
lines are crossed by another line the
pairs of angles on opposite sides of the
transversal but inside the two lines are
called Alternate Interior Angles.
a
b
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• Alternate Exterior Angles- When two
lines are crossed by another line the
pairs of angles on opposite sides of the
transversal but outside the two lines
are called Alternate Exterior Angles.
c
d
