our lesson today is about geometry. geometry has many branches. the first branch we shall consider is plane geometry -the study of points, lines and figures occurring in planes. just what do we mean by these terms a point is the simplest element in geometry. it has neither length nor thickness, which
is another way of saying that it no dimensions. we can represent a point by a dot made with a lead pencil or a piece of chalk. such a dot is not a geometry point but a physical point since it has length ,width and thickness. if these are two different point, the shortest distance between them is called a straight line. this line segment has only one dimension, called length; it does not have have width or thickness. a straight line that we draw on paper with a pencil has width and thickness. the name ray is given to the part of a line that starts at a given point . a plane figure formed by two rays is called an angle. in figure 2, there are two rays with the same starting point b . if two lines meet so that all the angles formed are equal, the lines are said to be perpendicular and the angles are called right angles. if two lines cross, the opposite angles are always equal. if an angle is less than a right angle-that is, if it has less than 90 degrees it is called acute.it is obtuse if it is greater than a right angle-that is, if it has more than 90. when the obtuse angle becomes so large that its sides from a straight line, it is a straight angle and has 180. an angle large than a straight angle is called a reflex angle. of course it must have more than 180. that's all for today. remember that you'll have an exam in geometry next week. if you revise today's lesson, you will get a good mark. if you don't, you may fait