Geometry: Lines and Angles |
 That by implication means that if we started drawing an angle from the top of the line BC and go all the way around to the bottom of the line (just bellow where we started, we would end up with a circle. This also means that since the top part of the straight line was 180 degrees, the bottom of the line will also be the same. Thus a full circle around the straight line will be: 2 x 180 = 360 degrees  Parallel lines and AnglesParallel lines as we saw in Introduction to Geometry are lines that move in the same direction and are the same distance from each other at every point along the line. You can see from the diagram bellow that the lines BCD and GFE are parallel to each other. Now here is something interesting with the relationship among angles created then both lines are crossed by the same straight line. You will see this in Geometry classes for a long time:  Some obvious things to Note here.Opposite angles in cases like this are always equal. For example Angles BCF and ACD are equal. The second thing to note is that Angles in the same position along the line crossing two parallel lines are also equal. This means Angles GFH and BCF are always equal.. Now let us take an example of how you solve for this missing angles if you have some of them given:  Here is how we solve for the missing Angles:  And the third rule bellow:  Now you can practice solving those questions using the two rules and the similarity rule. |
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