1. Welcome
GCSE Maths

3. Starter A
Draw a circle and mark a point A on its circumference. A B
Keep the compasses set at the size of the radius, and from point A draw an arc that cuts the circle at point B. A B
Repeat the process until six point are marked on the circumference. Join the points. What shape have you constructed?

4. Aims for this week
Use straight edge and a pair of compasses to do standard constructions.
Construct the perpendicular bisector of a given line.
Construct the perpendicular from a point to a line.
Construct the bisector of a given angle.
Construct a triangle.
KEYWORDS
Construct, circle, arc, vertex, two-dimensional, solid, angles, degree, bisect, perpendicular

5. PERPENDICULAR BISECTOR
Move your compasses to the end of the line
Make an arc above and below the line.
Repeat from the other end of the line.
Draw a line through the two sets of arcs.
Finished!! The two lines are at 90° to each other. Check if you like.

6. THE PERPENDICULAR FROM A POINT TO A LINE
Draw a straight line
Move your compasses to the point.
Draw an arc on the line either side of the point.
Move compasses to where the arc goes through the line.
Make an arc below the line.
Repeat other end of the line.
Now draw a line to connect the point and the arc.
Finished!! The point is 90° to the line. Check if you like.

7. ANGLE BISECTOR Move the compass to the meeting point of the lines.
Draw an arc on both lines
Move the compasses to each of the arcs on the lines in turn.
Make another arc in the general area of the bisector, (half way between the lines).
Repeat from the other arc.
Now draw a line from the end of your line through the arcs.
Finished. Check if you like.

8. THE PERPENDICULAR THROUGH A POINT ON A LINE
Move your compasses to the point. Open them up so they can cross over the line.
Draw two arcs on the line.
Move compasses to one of the arcs.
Draw an arc on the other side of the line roughly in the middle.
Repeat this from the other arcs. DO NOT CHANGE THE COMPASSES!
Now draw a line from the original point to this new crass (only the one line )

9. How to Construct a triangle using 3 different methods
Vocabulary
Compasses
Draw
Protractor
Arc
Construct
S S S (Side, side, side)
S S A (Side, side, angle)
S A A (Side angle, angle)

10. Side, side, side
1. Draw a line approximately 4cm Long and label it AB
2. Set your compasses to 5cm and with the point on A, draw an arc above the line AB. C
5cm
3. Set your compasses to 3cm and with the point on B, scribe an arc above the line AB. Where it crosses the other arc, call this point C
3cm B A
4cm
4. Draw the lines from A to C and B to C to complete the construction.
Note this is a special type of triangle. Measure angle B to find out.

11. Side, side, angle
1. Draw a line approximately 4cm Long and label it AB A
4cm B
2. Set the compasses to 5cm and with the compass point at A, draw an arc above the line AB
3. Place the protractor on the line so that the cross-hairs are over point A and the 0 – 180o line is covering the 4 cm line. Then mark a point at 50o

12. Side, side, angle continued
4. Remove the protractor and draw a line from A to the point you have just marked at 500 through the arc. Call this point C C
5cm
50o A
4cm B
5. Draw a line from point B to point C

13. Side, angle, angle
1. Draw a line approximately 4cm Long and label it AB A
4cm B
2. Place the protractor on the line so that the cross-hairs are over point A and the 0 – 180o line is covering the 4 cm line. Then mark a point at 50o in an anticlockwise direction

14. Side, angle, angle continued…
1. Draw a line approximately 4cm Long and label it AB
50o A
4cm B
2. Place the protractor on the line so that the cross-hairs are over point A and the 0 – 180o line is covering the 4 cm line. Then mark a point at 50o in an anticlockwise direction
3. From A draw a line to the mark just made and mark the angle as 50o
4. Now place the protractor on the line so that the cross-hairs are over point B and the 0 – 180o line is covering the 4 cm line. Then mark a point at 30o in a clockwise direction

15. Side, angle, angle continued…
5. From B draw a line to the mark just made and mark the angle as 30o C
50o
30o A
4cm B
6. Finally, where the two lines cross, mark that point C

16. Tringle construction

17. Reflection of the lesson
What did you learn new today?
Why did you learn it?
How are you going to remember it?