CK12 - Geometry

C. 3

D. 4

The secondpostulatelistedin this lessonstatesthat you can identifya planewith threenon-collinearpoints.
It is importantto label themas non-collinearpointssincethereare infinitelymanyplanesthat containcollinear
points.The answeris C.

Example 6

Whatgeometricfigurerepresentsthe intersectionof the two planesbelow?

A. point

B. line

C. ray

D. plane

The fifth postulatepresentedin this lessonsaysthat the intersectionof two planesis a line. This makes
sensefrom the diagramas well. It is a seriesof pointsthat extendsinfinitelyin both directions,so it is definitely
a line. The answeris B.

Drawingand Labeling

It is importantas you continueyour studyof geometryto practicedrawinggeometricshapes.Whenyou
makegeometricdrawings,you needto be sure to followthe conventionsof geometryso otherpeoplecan
“read”your drawing.For example,if you drawa line, be sure to includearrowsat both ends.With only one
arrow, it will appearas a ray, and withoutany arrows,peoplewill assumethat it is a line segment.Make
sure you labelyour points,lines,and planesclearly, and refer to themby namewhenwritingexplanations.
You will havemanyopportunitiesto honeyour drawingskillsthroughoutthis geometrycourse.

Example 7

Drawand labelthe intersectionof line and ray at point.

To beginmakingthis drawing,makea line with two pointson it. Labelthe points and.

Next,add the ray. The ray will havean endpoint and anotherpoint. The descriptionsaysthat the

ray and line will intersectat , so point shouldbe on. It is not importantfrom this descriptionin