CK12 - Geometry

D.Fill in the blank: = + _______.

E.Is the bisectorof Explainyour answer.

No. If bisected , then wouldbe Thatwouldmake but

Sometimeswe use specialmarksin diagrams.Tick marksshowcongruentsegments.Arc marksshow
congruentangles.Rightanglemarksshowright anglesand perpendicularlines and segments.

Whenthesesignsare used,the relationshipsthey representbecomepart of the giveninformationfor a
problem.

Example 2

Blue blobsare dots for pointsand singleand doublearc marksto showequalangles.

Basedon the markson the diagram,we knowthat:

(singletick marks).

(doubletick marks).

= (singlearc marks).

= (doublearc marks).

LessonSummary

As we moveforwardtowardmoreformalreasoning,we havereviewedthe basicpostulatesand expressed
themmoreformally. We saw that mostgeometricsituationsinvolvediagrams.In diagramswe can assume
somefacts,and we cannotassumeothers.

Pointsto Consider

In upcominglessonsyou will organizeyour reasoningpatterninto the two-columnproof.This is a traditional
patternthat still worksvery well today. It givesus a clear, directformat,and usesthe basicrulesof logic
that we saw in earlierlessons.We will provemanyimportantgeometricrelationshipscalledtheorems