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Conics. Conic Sections. (1) Circle. A circle is formed when i.e. when the plane is perpendicular to the axis of the cones. Conic Sections. (2) Ellipse. An ellipse is formed when
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Conic Sections (1) Circle A circle is formed when i.e. when the plane is perpendicular to the axis of the cones.
Conic Sections (2) Ellipse An ellipse is formed when i.e. when the plane cuts only one of the cones, but is neither perpendicular to the axis nor parallel to the a generator.
Conic Sections (3) Parabola A parabola is formed when i.e. when the plane is parallel to a generator.
Conic Sections (4) Hyperbola A hyperbola is formed when i.e. when the plane cuts both the cones, but does not pass through the common vertex.
y P(x,y) M(-a,0) O focus F(a,0) x Parabola A parabola is the locus of a variable point on a plane so that its distance from a fixed point (the focus) is equal to its distance from a fixed line (the directrix x = - a).
Form the definition of parabola, PF = PN standard equation of a parabola
axis of symmetry vertex latus rectum (LL’) mid-point of FM = the origin (O) = vertex length of the latus rectum = LL’= 4a
Ellipses An ellipse is the locus of a variable point on a plane so that the sum of its distance from two fixed points is a constant. P’(x,y) P’’(x,y)
major axis = 2a vertex lactus rectum minor axis = 2b length of semi-major axis = a length of the semi-minor axis = b length of lactus rectum =
Hyperbolas A hyperbola is the locus of a variable point on a plane such that the difference of its distance from two fixed points is a constant. P’(x,y)
transverse axis vertex lactus rectum conjugate axis length of lactus rectum = length of the semi-transverse axis = a length of the semi-conjugate axis = b
asymptote equation of asymptote :
Rectangular Hyperbola If b = a, then The hyperbola is said to be rectangular hyperbola.
If the rectangular hyperbola x2 – y2 = a2 is rotated through 45o about the origin, then the coordinate axes will become the asymptotes. equation becomes :
Simple Parametric Equations and Locus Problems x = f(t) y = g(t) parametric equations parameter Combine the two parametric equations into one equation which is independent of t. Then sketch the locus of the equation.
Equation of Tangents to Conics general equation of conics : • Steps : • Differentiate the implicit equation to find . • Put the given contact point (x1,y1) into • to find out the slope of tangent at that point. • (3) Find the equation of the tangent at that point.