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Geometry Terms
October 2007
Concentric
• Concentric circles share the same
centre
Converse
• Converse means the "if" and "then"
parts of a sentence are switched. For
example, "If two numbers are both even,
then their sum is even" is a true
statement. The converse would be "If
the sum of two numbers is even, then
the numbers are even," which is not a
true statement.
Write the converse of the
statement.
• If two chords on a circle are
equidistant from the centre of the
circle, then they are congruent.
• If two chords of a circle are
congruent, then they are
equidistant from the centre of the
circle
• If a statement and its converse are
both true, then they can be written
using iff, which means “if and only if”
• For example: the preceding example
can be written as
“Two chords on a circle are equidistant
from the centre of a circle iff they are
the same length.”
Or: “Two chords of a circle are the
same length iff they are equidistant
from the centre of a circle.”
Properties of Chords
• Chords that are equidistant from the
centre of a circle are equal in length
• Chords that are equal in length are
equidistant from the centre of a circle
• The perpendicular bisectors of two
chords pass through the center of the
circle
Proving triangles congruent
•Side - Angle – Side
•If two sides and the
included angle are
congruent to two sides
and the included angle
of a second triangle,
the two triangles are
congruent.
Side – Side - Side
•If three sides of one
triangle are congruent
to three sides of a
second triangle, the
two triangles are
congruent.
Angle – Angle - Angle
•If two angles and one
side of one triangle are
congruent to two
angles and the
included side of
another triangle, the
triangles are
congruent.
Angle – Angle - Side
•If two angles and a
nonincluded side of
one triangle are
congruent to two
angles and the
corresponding
nonincluded side of
another triangle, the
two triangles are
congruent.
Right angle – Hypotenuse - Side
•If two right triangles
have a hypotenuse
and a corresponding
congruent leg then
the triangles are
congruent.
Terms to remember
•Isosceles Triangle
•Vertical angles
•Corresponding
angles
•Transversal
•Alternate Interior
angles
•Supplementary
angles
•Co-interior angles
Answers
1. a)SSS
b) AAS
c) Not
d) Not
e) ASA
f) ASA