Geometry Angles Post 3

Three Hundred and Sixty

Many centuries ago the ancient Greeks decided to use the number 360 to represent a full spin.  Skateboarders know all about 360's and 180's.  Now in modern maths we use 360 as our standard.  It is really important that you know about this. 

Using A Protractor
This is a compulsory part of your unit - it will be in the test.
You just put the vertex/corner in the middle...


Can you see they have one line on zero?


pages 212-215 have these problems. 


Angles on a Straight Line
This is our first and most basic geometric rule.  A straight line is technically half a full spin.  The rule is "Angles on a straight line add to 180 degrees" nb this computer doesn't do degree symbol. 

Can you see that these two angles are on a straight line.  The size of a must be 180 minus 45.  So we would write the answer as a=135degrees. 

Exercise 14.7 on page 217 has these problems - there are 15 problems.  Do them all but you only need to draw/sketch five pictures (the rest answers only).