Vocabulary and Symbols

Remember -- Math is like a whole other language.  You have to know the vocabulary to be able to make your way around the problems.  I sent you home with the Vocabulary Quad sheet.  I hope you put it in a place where you look at it daily.

Also, we will encounter many new symbols in Geometry.  Here is a link to the Geometry Symbols you have in your binder in class.  Save this page or print it out so you can use it to help you when you are doing work at home.  

Points, Lines, Planes

Vocabulary you need to know:  point, line, plane, colinear, coplanar, intersecting

Here are some sites with examples you can use as you work at home.  You can watch them at your pace and replay them as often as you would like.

Definitions and examples of the vocabulary

Points, Lines and Planes by Konst Math

Finding Segment Length with Algebra by Algebra with

More examples on finding segment length using equations from Beacon Learning Center (good examples start on page 3)

Using Inductive Reasoning to make Conjectures -- Just a fancy way of saying you look at information and come to a conclusion.

The conclusions you make must be true - especially in Geometry.  No "well it looks like . . ." in Geometry.  

Those conclusions you make are usually worded as Conditional Statements.  Conditional statements usually follow a 

        If  _______________, then  __________________.
sort of pattern.  For example, some Conditional Statements could be:

  • If I don't wear my glasses, then I will not see well.
  • If it is not raining, then we will have a picnic.
  • If an angle measures less than 90 degress, then it is an acute angle.

Angles :   From this point until after Christmas remember these two numbers:  90 and 180.  They will be your best friends.

Vocabulary you need to know:  right, acute, obtuse, straight, complementary, supplementary, linear, vertical adjacent, vertex

Remember:  Whole - Part = Part

                           Part + Part = Whole

Angles with pictures and examples and some more here too.

Here is an example of Vertical Angles -- they are congruent (equal) in measure.  Remember them when you see them!  They will help make finding angle measures easier.

Angle examples and using Algebra to find missing measures.  This is another page with examples showing how to set up and solve equations to find angle measure.  

more from Khan Academy.  and this one on Complementary and Supplementary angles

AGAIN:  remember these two numbers:  90 and 180.  They will be your best friends.

Parallel lines cut by transversals

With this sort of image, you will either have ALL 90 degree angles - because the transversal is perpendicular to the parallel lines (like here):


they will be acute and obtuse (like here)

The angles formed are corresponding, alternate interior and alternate exterior.  This site shows examples of each.  

Here is an interactive site that will let you play around with the angle measures.


You already know that triangles have 3 sides and 3 angles.  BUT -- maybe you didn't know that there are different KINDS of triangles.

Also, all three angles in a triangle, any triangle, will always equal 180.  ALWAYS.