Summary on Angles

Summary on Angles

1. naming & classifying angles:

   • An angle is drawn with two arms and meets at the point called a vertex. To classify the angle you have to put the letters in order, but remember to always have the the letter at the vertex in the middle. correct answer: angle ABC incorrect answer: angle BCA

2. measuring & drawing angles:

   • to measure angles you use an instrument called a protractor. when measuring keep the point straight and depending on what size the angle you use the inside and/or the outside numbers.

3. complementry & supplementry angles:

   • complementry angles are angles that add up to 90 degrees. e.g. 45+45=90 or 30+60=90. supplementry angles are angles that add up to 180 degrees. e.g. 90+90=180 or 100+80=180

4. angles at a point and vertically opposite angles:

   • angles at a point (in a revolution) add up to 360 degrees. A special case of angles at a point occurs when two straight lines cut each other. Vertically opposite angles are equal. e.g. x=2 and w=y or x=30 and y=30.

5. angles on parallel:

   • parallel lines are lines that are the same distance apart and never intersect. There is 3 different types of angles on parallel lines. 1. corresponding- these angles are equal remember this as the letter 'F'. 2. alternate angles. these angles are also equal. remember as the letter 'U'. 3. co- interior. this type of angle has to add up to 180 degrees exactly. e.g 100=80= 180 degrees. remember this as the letter 'Z'.

6. proving parallel lines:

   • we can use what we know about angles and parallel lines to prove that two lines are parallel. if two lines are parallel if: alternate angles are equal or corresponding angles are equal or co-interior angles are supplementry.