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CHAPTER VII LINES AND ANGLES. POSITION OF TWO LINES. H G segments AB and CD E F are two parallel lines
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POSITION OF TWO LINES H G segments AB and CD E F are two parallel lines D C AB and BC are two A B intersecting lines AB and EH are two skew segments ( neither parallel nor intersecting)
Definition of an angle A Legs, AB and BC B components of the angle C . Two sides ( legs ) Vertex . Vertex . The area the area of angle
TYPES OF ANGLES 1. Right angle : an angle with the measure of 90 • Acute angle : an angle with the measure is less than 90 3. Straight angle : angle with the measure of 180
4. Obtuse angle : an angle with the measure is greater than 90 but less than 180 5. Reflection angle : an angle with the measure is greater than 180
CONSTRUCTING ANGLES • Dividing an angle into two equal part a. Draw an arc using a protractor with O as the centre so that the arc intersects OA at C and OB at D b. Consider, then draw an arc with C as the centre and the radius i similar to step 2. do the same with D . You will get two arc intersects at a point in region AOB. Give P as the name of the point. c. Connect O to P
B D P O A C
THE PROPERTIES OF LINES • Straight lines 2. Horizontal lines 3. Vertical lines 4. Parallel lines
5. Intersection lines • Superimpose lines • Perpendicular lines 8. Skew lines
THE RELATIONSHIP BETWEEN ANGLES AND LINES Alternate interior angles 1 2 5 6 ∠ 2 and ∠ 7 ∠ 4 and ∠ 5 3 4 7 8 Alternate exterior angles ∠ 1 and ∠ 8 ∠ 3 and ∠ 6 Corresponding angles ∠ 1 and ∠ 5 Suplementary interior angles ∠ 3 and ∠ 7 ∠ 4 and ∠ 7 ∠ 2 and ∠ 5 ∠ 2 and ∠ 6 ∠ 4 and ∠ 8 Suplementary exterior angles ∠ 1 and ∠ 6 ∠ 3 and 8