Polytechnic · Technical Drawing · Interactive drawing lesson

The centre of a given arc or circle

Recover a lost centre from two chords. Learn the centre of a given arc or circle step by step in an interactive Polytechnic technical drawing lesson.

What you will learn

This guided practical demonstrates the construction on a drawing board and explains the method in a clear sequence.

Open the interactive drawing lesson

More Technical Drawing lessons

• Bisecting a line — Find the middle of a line.
• A perpendicular from a given point to a line — Square up from a point on a line.
• A line divided into proportional parts — Split a line into equal parts.
• A perpendicular from any point to a line — Drop a square line onto a line.
• Parallel lines — Draw lines that never meet.
• Bisecting an angle — Cut an angle in half.
• Various angles constructed without a protractor — Build angles with a compass only.
• A copied angle — Copy an angle without measuring.
• The centre of a given arc or circle — Recover a lost centre from two chords.
• Various geometrical shapes — Shapes drawn inside one circle.
• Straight lines joined to curves by an arc — Join a line to a curve smoothly.
• An ellipse and scales — Draw an ellipse and a plain scale.
• First angle orthographic projection — Front view, plan and end view.
• Isometric drawing — Draw a solid on three axes.
• Bars — Round, square and hex bar with breaks.
• Tubes — Show a bore through a broken tube.
• Shafts — Stepped shaft with chamfer and keyway.
• Compression springs — Coils drawn between two envelope lines.
• Tension springs — Closed coils with end loops.
• Splined shafts (external) — Splines on the outside of a shaft.
• Splined shafts (internal) — Splines cut inside a bore.
• Serrated shafts (external) — Fine serrations round a shaft.
• Serrated shafts (internal) — Serrations inside a clamped boss.
• Functional dimensioning — Dimension the sizes that make it work.
• Non-functional dimensioning — Size the rest of the part.
• Auxiliary dimensioning — Reference sizes shown in brackets.
• Chain dimensioning — Sizes taken end to end.
• Datum dimensioning — Every size from one face.
• Types of line — Outline, hidden, centre and break lines.
• Freehand letters and numerals — Print neatly between guide lines.
• Bold lettering for title blocks — Head up a drawing sheet.
• Basic assembly drawings — Parts drawn together and ballooned.
• Exploded diagrams — Pull the parts apart on one axis.
• Orthographic from a pictorial drawing — Turn a 3D view into three views.
• Third angle projection — Plan above, end view on the left.
• Freehand sketches in first angle — Sketch three views without instruments.
• Isometric circles — Four-centre circles on a sloping face.
• Isometric ellipses — Ellipses on all three faces.
• The isometric scale — Shorten true lengths for isometric.
• Sectioned diagrams in first angle — Cut a part and hatch the cut face.
• Hydraulic power steering — Pump, relief valve, control valve and ram.
• Hydraulic power brakes — Pressure supply to the wheel cylinders.
• Hydraulic tipping mechanisms — Raise and lower a tipping body.
• Heavy vehicle air brakes — Compressed air to the brake chambers.
• Basic auto-electrical circuits — Battery, fuse, switch and earth return.