Conic Sections
Procedure
1. To draw a parabola with a given distance of focus from the directrix. Also, draw a normal and a tangent at a given point from the directrix.
- Draw the axis AB and directrix CD perpendicular to each other.
- Mark the point as focus F at a distance given from the directrix.
- Mark the vertex V on the axis such that VF= AV.
- From V, draw a perpendicular line VE whose length is equal to VF.
- Join VE with point A and produce the line such that the eccentricity is equal to 1.
- Mark points 1, 2,3, 4, 5 and so on to the right-hand side of V.
- Through each of the points, raise perpendicular lines meeting AE at points 1’,2’, 3’,4’, 5’ and so on.
- Take a radius of 1-1’ and with F as the centre, draw arcs on the line for the first point on either side of the axis. Mark the points as P1 and P1’ respectively.
- Repeat the same procedure for the rest of the points.
- Join all the points obtained by marking off arcs. The smooth curve so obtained is the required parabola.
- Locate the point in the parabola where the tangent and normal has to be drawn.
- Join the point with the focus. Draw a line perpendicular to it such that it's one end touches the directrix. Mark it as T.
- From T, draw a line passing through the desired point and extend it. This is the required Tangent.
- Draw a line on the desired point that is perpendicular to the tangent. This is the required normal.
2. To draw an ellipse with a given distance of focus from the directrix having an eccentricity equal to 2/3. Also, draw a tangent and normal at a given point from the directrix.
- Draw the axis AB and directrix CD perpendicular to each other.
- Mark the point as focus F at a distance given from the directrix.
- Divide AF into five equal segments.
- Locate the vertex V from the third division from point A or from second division from point F. So the eccentricity e= 2/3.
- From the vertex draw a perpendicular line VE that is equal to VF. Join AE and extend it.
- Mark points 1, 2,3, 4, 5 and so on to the right-hand side of V.
- Through each of the points, raise perpendicular lines meeting AE at points 1’,2’, 3’,4’, 5’ and so on.
- With a radius of 1-1’ and having F as the centre, mark arcs on the line for the first point on either side of the axis. Mark the points as P1 and P1’ respectively.
- Correspondingly, locate the points P2, P2’, P3, P3’ and so on.
- A closed curve is formed by joining all the points which is the required ellipse. It has two directories and two foci.
- Mark the point in the ellipse where the tangent has to be constructed.
- Join the point with the focus and draw a line perpendicular to it. Name its one end as T.
- Draw a line from T, passing through the point and extend it. This is the required tangent.
- Draw a line perpendicular to the tangent on the desired point. This is the required normal.
3. To draw a hyperbola at a given distance of focus from the directrix having an eccentricity equal to 3/2. Also, draw a normal and a tangent at a given point from the directrix.
- Draw the axis AB and directrix CD perpendicular to each other.
- Mark the point as focus F at a distance given from the directrix.
- Divide AF into 5 equal parts.
- Mark the vertex V on the point from the third division of focus. Draw a perpendicular line VE whose length is equal to VF.
- Join AE and produce the line.
- From V locate points 1, 2, 3 and so on, on the axis.
- Draw perpendicular lines from each of the points meeting the line AE at points 1’,2’, 3’ and so on.
- Take 1-1’ as the radius and have F as the centre draw arcs on each of the lines on either side of the axis.
- Obtain the points P1, P1’, P2, P2, and so on.
- Join all the points and curve so obtained is a hyperbola.