How to Construct a Right-Angle

What you Need

You will need:-

	(a)	Some Sheets of Plain A4 Paper
	(b)	A 25cm Ruler
	(c)	A 0.5mm Clutch Pencil
		or
		An Ordinary B-grade Pencil
		A Block of Draftsman's Sandpaper
	(d)	A Pair of Good Quality Compasses

You may also want a:-

(e)

Protractor

for checking your angles.

Bisection of a Semicircle

(A)		Draw a line about 20mm from the long edge of a sheet of paper
(B)		Use a compass point to make a small hole in the approximate center of the line ( Point 1 )
(C)		Draw a semicircle about Point 1
(D)		Without changing the compass span
		Place the compass point at Intersection 2 and draw the arc a
(E)		Still keeping the set compass span
		Place the compass point at Intersection 3 and draw the arc b
(F)		Placing your compass point at Point 3 and then Point 4,
		draw the intersecting arcs c and d
(G)		Join the arcs' intersection 5 to Point 1 with ruler and pencil
		The angles AA and AB are both right angles

An Angle Within a Semicircle

(A)		Draw a line about 20mm from the long edge of a sheet of paper
(B)		Use a compass point to make a small hole in the approximate center of the line ( Point 1 )
(C)		Draw a semicircle about Point 1
(D)		Draw a second line between Point 2 and any position on the semicircle
(E)		Connect the Point 3 where the second line touches the semicircle with Point 4,
		which is diametrically opposite Point 2
		Angle AC is a right angle