Lesson Notes By Weeks and Term v4 - SHS 1
SPATIAL SENSE
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SPATIAL SENSE
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Subject: Additional Mathematics
Class: SHS 1
Term: 2nd Term
Week: 4
Grade code: 1.2.1.LI.7
Strand code: 2
Sub-strand code: 1
Content standard code: 1.2.1.CS.1
Indicator code: 1.2.1.LI.7
Theme: GEOMETRIC REASONING AND MEASUREMENT
Subtheme: SPATIAL SENSE
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This lesson introduces the concept of finding the angle between two intersecting straight lines. In our daily lives in Ghana, we see intersecting lines everywhere – from the way roads cross at junctions like the Ako Adjei Interchange in Accra, to the patterns in Kente cloth, to the structural supports in the roof of a house. Being able to accurately determine the angles at these intersections is a fundamental skill in many fields, including engineering, architecture, surveying, and even computer graphics. Today, we will move beyond manual calculations and protractors to use a powerful and modern technological tool, GeoGebra, to explore and determine these angles precisely.
A. Intersecting Lines and Angles
When two straight lines cross each other, they are called intersecting lines. They meet at a single, common point called the point of intersection.
When these two lines intersect, they form four angles at the point of intersection.
Let's look at the properties of these angles: Vertically Opposite Angles: Angles that are directly opposite each other are equal. In the diagram above, Angle `a` = Angle `c`, and Angle `b` = Angle `d`. Angles on a Straight Line: Angles that lie on a straight line add up to 180°. So, `a + b = 180°`, `b + c = 180°`, `c + d = 180°`, and `d + a = 180°`. B. Acute and Obtuse Angles An acute angle is an angle that is less than 90°. An obtuse angle is an angle that is greater than 90° but less than 180°.