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# GEOMETRIC CONSTRUCTION: TANGENTS OF A CIRCLE

## Tangent and Normal to a Circle

A tangent is a straight line that touches the circumference of a circle. It is usually at right angles to the radius of the circle.

A normal is a straight line which joins the center of a circle to the tangent at the point of tangency.

Evaluation

Draw a circle indicating its tangent and normal to the tangent

## Construction of Tangent and Normal to a circle

### Tangent to a circle from a point on the circumference

Steps

1. Draw the circle with center O
2. Mark the given point A on the circumference
3. Join OA and extends it outwards
4. With A as center and radius OA, draw an arc to cut the extended line at B
5. The perpendicular bisector of OB is the required tangent
6. CD is the tangent to the circle at point A while OB is the normal ### Tangent to a circle from a given point outside the circle

Steps

1. Draw the given circle with center O
2. Locate point A outside the circle
3. Draw line OA
4. Construct a semicircle on OA to intersect the given circle at B
5. Line AB is the required tangent to the circle Tangent to a circle from a given point outside the circle

### Tangent to two Equal Circles

Steps

1. Draw the two circles with centers A and B respectively
2. Draw line AB to join the two centers
3. Draw a line perpendicular to AB at A to intersect the first circle at D
4. Draw a line perpendicular to AB at B to intersect the second circle at C
5. CD is the required tangent EVALUATION

1. Construct a tangent to a circle of radius 4cm at any point on the circumference.

Lesson tags: Basic Technology Lesson Notes, Basic Technology Objective Questions, JSS2 Basic Technology, JSS2 Basic Technology Evaluation Questions, JSS2 Basic Technology Evaluation Questions First Term, JSS2 Basic Technology First Term, JSS2 Basic Technology Objective Questions, JSS2 Basic Technology Objective Questions First Term
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