Chapter 16

Plane Figures

By: Brittany Bolter (smartest girl EVER!):]

Lesson one:Points, lines, and line segments

• Line segment- – Section of a line– Bounded by two endpoints

Endpoints

Line segment

R TSay: line segment RT or Line segment TR

Write: RT or TR

• Parallel-– Lines that are ALWAYS the same distance

apart– They will NEVER touch

B

C

ED

Say: line BE is parallel to line CD

Write: BE l l CD

This symbol means “is parallel to”

• Intersecting-– Lines the cross over each other

E

HF

G

Say: line EF and line GH intersect at point J

J

• Perpendicular-– two lines that form right angles

Say: line PQ is perpendicularTo line TV Write: PQ TV

T

P Q

V

This symbol means “Is perpendicular too”

• Right Angle– an angle that has a measurement of 90 – Makes a square in the corner

90

Lesson two:Rays and Angles

• Ray-– A line that has a starting point but no endpoint

Say: ray BC

Write: BCB

C

• Angle-– The amount of turning

between two lines meeting at a common point

– Formed by two rays with a common endpoint B

C

D

Say Write

Angle c

C

Angle DCB

DCB

Angle BCD

BCD

When naming an Angle, the vertexIs the middle letter.

• Sides-– One of the rays make up an angle

Sides

• Vertex-– The common endpoint of the angle– Where the two rays meet

Vertex

***When naming an angle, the Vertex is the middle letter.

Example: angle ABC

A

B C

• Right angle-– An angle whose measurement is 90– Makes a square in the corner

• Obtuse angle – An angle greater than a right angle– Any angle between 90 and 180

• Acute angle-– An angle less than a right angle– Any angle measurement less than 90

• Straight angle-– Angle that forms a straight angle– Any angle that equal 180

Lesson three:measure angles

• Degrees-– A unit for measuring the size of an angle– Written as

• Protractor-– Instrument used to measure angles

How to use a protractor

• Step 1: place the center mark of the protractor on vertex

• Step 2: Align the 0 mark of one of the protractor scales with one ray of the angle to be measured