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1-5 – Postulates and Theorems Relating Points, Lines, and Planes. Terms. ________________________ – a basic assumption accepted without proof ________________________ – a statement that can be proved using postulates, definitions, and previously proved theorems
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1-5 – Postulates and Theorems Relating Points, Lines, and Planes
Terms • ________________________ – a basic assumption accepted without proof • ________________________ – a statement that can be proved using postulates, definitions, and previously proved theorems • ________________________ – there is at least one • ________________________ – there is no more than one • ________________________ – exactly one • ________________________ – to define or specify
Postulates • What Postulates have we discussed so far?
Postulates Postulate 5 – a line contains at least two points; a plane contains at least three points not all in one line; space contains at least four points not all in one plane.
Postulates Postulate 6 – Through any two points there is exactly one line.
Postulates Postulate 7 – Through any three points there is at least one plane, and through any three noncollinear points there is exactly one plane.
Postulates Postulate 8 – If two points are in a plane, then the line that contains the points is in that plane.
Postulates Postulate 9 – If two planes intersect, then their intersection is a line.
Theorems Theorem 1-1 – If two lines intersect, then they intersect in exactly one point.
Theorems Theorem 1-2 – Through a line and a point not in the line there is exactly one plane.
Theorems Theorem 1-3 – If two lines intersect, then exactly one plane contains the lines.
Name the Postulate/Theorem • Relationships between points • Two points must be collinear • Three points may be collinear or noncollinear • Three points must be coplanar • Three noncollinear points determine a plane • Four points may be coplanar or noncoplanar • Four noncoplanar points determine space • Space contains at least four noncoplanar points
Name the Postulate/Theorem • Three ways to determine a plane • Three noncollinear points determine a plane • A line and a point not on the line determine a plane • Two intersecting lines determine a plane
Relationships between two lines in the same plane Either two lines are parallel, or they intersect. Example:
Relationship between a line and a plane Either a line and a plane are parallel, or they intersect in exactly one point, or the plane contains the line. Example:
Relationships between two planes Either two planes are parallel, or they intersect in a line. Examples:
Practice • Name a plane that contains . • Name a plane that contains but is not shown in the diagram. • Name a plane that contains and . • Name a plane that contains and . W V T U S R P Q
Practice • Name the intersection of plane TWRQ and plane PSWT. • Name five lines in the diagram that don’t intersect plane UVRQ. • Name one line that is not shown in the diagram that does not intersect plane UVRQ. • Name three planes that don’t intersect and don’t contain . W V T U S R P Q