Page 34 - ENGINEERING DRAWING

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ii. Bisect GA.

o
iii. From A, construct an angle of 45 to intersect the bisector at point 4.
o
iv. From A, construct an angle of 60 to intersect the bisector at point 6.
v. Bisect between points 4 and 6 to give point 5. Point 4 is the centre of a circle
containing a square. Point 5 is the centre of a circle containing a pentagon. Point 6
is the centre of a circle containing a hexagon. By marking off points at similar
distances the centres of circles containing any regular polygon can be obtained.

vi. Mark off point 7 so that 6 to 7 = 5 to 6 (=4 to 5).

vii. With centre at point 7 draw a circle, radius 7 to A (= 7 to G).

viii. Step off the sides of the figure from A to B, B to C, etc.

ABCDEFG is the required heptagon.

e. Construct a regular Octagon is a diagonal size.

Steps of construction:

i. Draw the circle and insert a diameter AE.

ii. Construct another diagonal CG, perpendicular to the first diagonal.

Iii. Bisect the four quadrants thus produced to cut the circle in B, D, F and H.

iii. ABCDEFGH is the required octagon.