1. Geometry 1
J.Byrne 2017

2. Geometry involves the study of angles, points, lines, surfaces & solids
An angle is formed by the intersection of two straight lines. This angle below is called abc with b as the vertex.
If you imagine lines a & b are the hands of a clock and the line a was to move in one complete circle until it was back to its original position. It will have made 1 full revolution.
A revolution is 360°
Half revolution is 180°
Quarter revolution is 90° a b c
J.Byrne 2017

3. An acute angle is less than 90°
Types of angles
An acute angle is less than 90°
A right angle is 90°
J.Byrne 2017

4. An obtuse angle is more than 90 °
Types of angles
An obtuse angle is more than 90 °
A reflex angle is greater than 180° but less than 360°
J.Byrne 2017

5. If two angles add up to 90° they are called complimentary angles
Types of angles
If two angles add up to 90° they are called complimentary angles
If two angles add up to 180° they are called supplementary angles
If two straight lines are running on the same surface and equal distance apart they are called Parallel lines they will never cross
J.Byrne 2017

6. Transversals & Parallel Lines
Opposite angles are equal A = B
Corresponding angles are equal A = C
Find the angles below
B = 125° A = 125° C = 125° A B C
120°
60°
60°
60°
120° B
55° A C
J.Byrne 2017

7. Draw a line any length call it a,b.
Bisecting a line
Draw a line any length call it a,b.
Set compass to more than half the line length swing an arc above and below the line from both points a & b
The arcs cross both above and below the line.
Draw a line where the arcs intersect This line is called the bisector.
J.Byrne 2017

8. Draw an arc from the vertex point b on both lines.
Bisecting an angle
Draw an arc from the vertex point b on both lines.
The arcs intersect at points a & c
Set the compass again and swing an arc from points a & c
Draw a line from the vertex to point of intersection.
This line is called the bisector
J.Byrne 2017

9. Perpendicular & Parallel lines
Draw a perpendicular line from point P to line ab
From point P swing an arc to touch line ab at points 1 & 2
Swing an arc from points 1 & 2
Draw a line from point P to point of intersection.
J.Byrne 2017

10. Divide line ab into 3 equal parts
Dividing Lines
Divide line ab into 3 equal parts
Draw a light line any length and angle from point a.
Using a compass step off 3 times
Join up the last arc to point b.
Using both set squares draw lines parallel to last line at each of the arcs
J.Byrne 2017

11. Construct a triangle from line ab in the ratio of 2: 3 : 4
Ratios in Geometry
Construct a triangle from line ab in the ratio of 2: 3 : 4
Divide line ac into 9 equal parts
Draw a parallel line at point 2 & 5
Line ab is now in the ratio of 2: 3 : 4
Using side 3 as the base swing up point a and point b from either corner
Join up each corner to where the arcs intersect
J.Byrne 2014

12. Q 1 What are the angles at A,B & C
Revision Lesson 1
Q 1 What are the angles at A,B & C
Q 2 What are the angles at A,B & C
Q 3 Name the angles below
J.Byrne 2014

13. Q 4 Redraw the shape below the steps are equally spaced
Revision Lesson 1
Q 4 Redraw the shape below the steps are equally spaced
Q 5 Construct a triangle having a perimeter of 175 with sides in the ratio of 3: 4 : 3
Q 6 Construct a triangle having a perimeter of 175 with sides in the ratio of 4: 2 : 5
J.Byrne 2014