TOPIC: TANGENCY (PRINCIPLE OF TANGENCY)
Tangent is a straight line which touches the circumference of a cicle extended at a point. This is identified at point of tangency.
The application of tangency can be noticed very readily in all aspects of engineering, construction, especially in the production of engine parts like gaskets, hooks, spanners, knobs, electrical bulb among others.
TO CONSTRUCT A TANGENT AT A POINT ON THE CIRCUMFERENCE
1. Draw the given circleat at the given centre O.
2. Locate the given point of tangency on the circumference.
3. Centre at P, radius PO, draw a semicircle to cut OP produced at X.
4. Bisect line OX to get the tangent(bisector) at P.
R = 40
TO CONSTRUCT PARALLEL OR COMMON TANGENTS TO TWO CIRCLES OF EQUAL RADII
1. Draw the given circles with centres at O1 and O2.
2. Join the centres O1 and O2 with a straight line.
3. Construct perpendicular line at O1 and O2.
Lines X-X and Y-Y at right angles to the perpendicular and tangential to the circles are the parallel tangents.
R = 35 and /O1-O2/= 80