lines and angles

• Line with two end points - line-segment

• A part of a line with one end point - ray

• If three or more points lie on the same line, they are called collinear points; otherwise they are called non-collinear points.

• Angle is formed when two rays originate from the same end point.

• The rays making an angle are called the arms of the angle and the end point is called the vertex of the angle.

• Acute angle : 0° < x < 90°

• Right angle : y = 90°

• Obtuse angle : 90° < z < 180°

• Straight angle : s = 180°

• Reflex angle : 180° < t < 360°

• Complementary Angles : sum of 2 angel= 90°

• Supplementary Angles : sum of 2 angel= 180°

If a ray stands on a line, then the sum of the two adjacent angles so formed is 180° and vice-versa. This property is called as the Linear pair axiom.

If two lines intersect each other, then the vertically opposite angles are equal.

Lines which are parallel to a given line are parallel to each other.