b iconditionals and definitions big idea: reasoning and proof essential understandings: a definition...
TRANSCRIPT
![Page 1: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/1.jpg)
BICONDITIONALS AND DEFINITIONS
BIG IDEA: REASONING AND PROOF
ESSENTIAL UNDERSTANDINGS:• A definition is good if it can be written as a
biconditional.• Every biconditional can be written as two
conditionals that are converses of each other.
MATHEMATICAL PRACTICE:
Attend to precision
![Page 2: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/2.jpg)
GETTING READY Look at the examples of insects and
noninsects below. How would you complete the following sentence: “If an animal is an insect, then . . . ? Explain your reasoning.
![Page 3: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/3.jpg)
MATH BACKGROUND
The first terms learned in Geometry must be understood and undefined. The terms that follow can be explained using only undefined terms or a combination of undefined terms and previously defined terms.
Postulates are assumed to be true without proof, and theorems are proved using postulates and previously proved theorems.
![Page 4: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/4.jpg)
DEFINITIONS
All definitions can be interpreted “forward” and “backward”.
Vertical Angles: Two angles whose sides form two pairs of opposite rays. Two pairs of opposite rays form the sides of two angles.
Angle Bisector: A ray that divides an angle into two adjacent angles that are
congruent. Two adjacent angles that are congruent in an angle divided by
a ray.
Perpendicular Lines: Two lines that intersect to form a right angle. Two lines that form a right angle are perpendicular.
![Page 5: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/5.jpg)
EX 1: USE THE DIAGRAM TO DETERMINE WHETHER THE STATEMENT IS TRUE OR FALSE
a) Points O, P and Q are collinear.
b) are supplementary
c) is perpendicular to
d) are complementary
e) Point Q is between point O and point P
f) are vertical angles
and MPO NQP
MP;<<<<<<<<<<<<< <
NQ;<<<<<<<<<<<<< <
and MPO MPQ
and LMO KMN
![Page 6: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/6.jpg)
BICONDITIONAL STATEMENT
The combination of a _________________________ statement and its ____________________. A biconditional contains the words “ _________ and ____________ __________”.
EX: A point is a midpoint if and only if it divides a segment into two congruent segments.
If a point is a midpoint, then it divides a segment into two congruent segments
If a point divides a segment into two congruent segments, then it is a midpoint.
and as p q q p p q
![Page 7: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/7.jpg)
EX 2: REWRITE THE BICONDITIONAL STATEMENT AS A CONDITIONAL AND ITS CONVERSE STATEMENTS.
a) Two lines intersect if and only if their intersection is exactly one point.
b) Two angles are supplementary if and only if the sum of the measures of the two angles is .
180
![Page 8: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/8.jpg)
EX 3: THE FOLLOWING STATEMENT IS TRUE. WRITE THE CONVERSE AND DECIDE WHETHER IT IS TRUE OR FALSE. IF THE CONVERSE IS TRUE, COMBINE TO FORM A BICONDITIONAL
a)
b)
2If 49, then 7.x x
2If 4, then 2 or 2.x x x
![Page 9: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/9.jpg)
GOOD DEFINITION A good definition is a statement that can help you
identify or classify an object. A good definition has several important components. It uses clearly understood terms. These terms should be
commonly understood or already defined. It is precise. Good definitions avoid words such as large, sort
of, and almost. It is reversible. That means you can write a good definition
as a true biconditional.
Which of the following are good definitions?
a) A fish is an animal that swims.b) Giraffes are animals with very long necks.c) A square is a figure with four right anglesd) A penny is a coin worth one cent.e) Perpendicular lines are two lines that intersect to form right
angles.
![Page 10: B ICONDITIONALS AND DEFINITIONS BIG IDEA: REASONING AND PROOF ESSENTIAL UNDERSTANDINGS: A definition is good if it can be written as a biconditional. Every](https://reader036.vdocuments.mx/reader036/viewer/2022083009/5697bfd51a28abf838cad3a8/html5/thumbnails/10.jpg)
2.2 P. 8214 – 42 EVENS, 51 – 54 ALL, 5620 questions