{"id":3829,"date":"2021-08-09T08:19:55","date_gmt":"2021-08-09T08:19:55","guid":{"rendered":"https:\/\/mathemerize.com\/?p=3829"},"modified":"2022-02-15T22:49:47","modified_gmt":"2022-02-15T17:19:47","slug":"different-types-of-parabola","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/different-types-of-parabola\/","title":{"rendered":"Different Types of Parabola Equations"},"content":{"rendered":"
Here, you will learn Different Types of Parabola and Standard equations of parabola, focal chord, double ordinate and latus rectum of parabola.<\/p>\n
Let’s begin –<\/p>\n
A parabola is the locus of a point which moves in a plane, such that its distance from a fixed point(focus) is equal to its perpendicular distance from a fixed straight line(directrix).<\/p>\n
The Standard equation of parabola is \\(y^2 = 4ax\\) <\/strong>and it is shown in figure. For this parabola :<\/p>\n (i) Vertex<\/strong> is (0,0).<\/p>\n (ii) focus<\/strong> is (a,0)<\/p>\n (iii) Axis<\/strong> is y = 0<\/p>\n (iv) Directrix<\/strong> is x + a = 0<\/p>\n (a) Focal distance :<\/strong><\/p>\n The distance of a point on the parabola from the focus is called the focal distance of the point.<\/p>\n (b) Focal chord :<\/strong><\/p>\n A chord of the parabola, which passes through the focus is called a focal chord.<\/p>\n (c) Double ordinate :<\/strong><\/p>\n A chord of the parabola perpendicular to the axis of the symmetry is called double ordinate.<\/p>\n (d) Latus rectum :<\/strong><\/p>\n A double ordinate passing through the focus or a focal chord perpendicular to the axis of parabola is called latus rectum.<\/p>\n For \\(y^2 = 4ax\\).<\/p>\n Length of the latus rectum = 4a<\/p>\n Length of the semi latus rectum = 2a<\/p>\n Ends of the latus rectum are L(a, 2a) & L'(a, -2a).<\/p>\n<\/blockquote>\n Note :<\/strong><\/p>\n (i) Perpendicular distance from focus on the directrix = half the latus rectum.<\/em><\/p>\n (ii) Vertex is middle point of the focus & point of intersection of directrix & axis.<\/em><\/p>\n (iii) Two parabolas are said to be equal if they have the same latus rectum.<\/em><\/p>\n Four different types of parabola equations are<\/p>\n \\(y^2\\) = 4ax ; \\(y^2\\) = -4ax ; \\(x^2\\) = 4ay ; \\(x^2\\) = -4ay.<\/p>\n<\/blockquote>\n One I had shown above and three others are shown below.<\/p>\n\n\n \\(y^2\\) = -4ax<\/b><\/p>\n\t\t\t <\/div>\n\t\t\t \\(x^2\\) = 4ay<\/b><\/p>\n\t\t\t <\/div>\n\t\t\t \\(x^2\\) = -4ay<\/b><\/p>\n\t\t\t <\/div>\n\t\t\t<\/div> Example : <\/span> Find the vertex, axis, directrix, focus, latus rectum and the tangent at vertex for the parabola \\(9y^2 – 16x – 12y – 57\\) = 0.<\/p>\n Solution : <\/span>The given equation can be written as \\(({y-2\\over 3})^2\\) = \n\t\t \\(16\\over 9\\)\\(({x + 61\\over 16})\\) which is of the form \\(y^2\\) = 4ax. Hence the vertex is (-\\(61\\over 16\\), \\(2\\over 3\\)) Position of a point relative to a parabola :<\/strong><\/p>\n The point (\\(x_1\\),\\(y_1\\)) lies outside, on or inside the parabola \\(y^2\\) = 4a\\(x_1\\) is positive, zero or negative.<\/p>\n Find the value of k for which the point (k-1, k) lies inside the parabola \\(y^2\\) = 4x.<\/a><\/p>\n\n
Different Types of Parabola & Standard Equations of Parabola<\/h2>\n
\n
\n\n\n\n\n\t\t
\n\t\t Parabola<\/th>\n\t\t Vertex<\/th> \n\t\t Focus<\/th>\n\t\t Axis<\/th>\n\t\t Directrix<\/th>\n\t\t <\/tr>\n\t\t \n\t\t \\(y^2\\) = 4ax<\/td>\n\t\t (0,0)<\/td> \n\t\t (a,0)<\/td>\n\t\t y = 0<\/td>\n\t\t x = -a<\/td>\n\t\t <\/tr>\n\t\t \n\t\t \\(y^2\\) = -4ax<\/td>\n\t\t (0,0)<\/td> \n\t\t (-a,0)<\/td>\n\t\t y = 0<\/td>\n\t\t x = a<\/td>\n\t\t <\/tr>\n\t\t \n\t\t \\(x^2\\) = +4ay<\/td>\n\t\t (0,0)<\/td> \n\t\t (0,a)<\/td>\n\t\t x = 0<\/td>\n\t\t y = -a<\/td>\n\t\t <\/tr>\n\t\t \n\t\t \\(x^2\\) = -4ay<\/td>\n\t\t (0,0)<\/td> \n\t\t (0,-a)<\/td>\n\t\t x = 0<\/td>\n\t\t y = a<\/td>\n\t\t <\/tr>\n\t\t \n\t\t \\((y-k)^2\\) = 4a(x-h)<\/td>\n\t\t (h,k)<\/td> \n\t\t (h+a,k)<\/td>\n\t\t y = k<\/td>\n\t\t x+a-h = 0<\/td>\n\t\t <\/tr>\n\t\t \n\t\t \\((x-p)^2\\) = 4b(y-q)<\/td>\n\t\t (p,q)<\/td> \n\t\t (p,b+q)<\/td>\n\t\t x = p<\/td>\n\t\t y+b-q = 0<\/td>\n\t\t <\/tr>\n\t\t <\/tbody><\/table>
\n\n\t\t \n\t\t
\n\t\t Length of Latus rectum<\/th>\n\t\t Ends of Latus rectum<\/th>\n\t\t Parametric equation<\/th>\n\t\t Focal length<\/th>\n\t\t <\/tr>\n\t\t \n\t\t 4a<\/td>\n\t\t (a,\\(\\pm\\)2a)<\/td> \n\t\t (a\\(t^2\\), 2at)<\/td>\n\t\t x + a<\/td>\n\t\t <\/tr>\n\t\t \n\t\t 4a<\/td>\n\t\t (-a,\\(\\pm\\)2a)<\/td> \n\t\t (-a\\(t^2\\), 2at)<\/td>\n\t\t x – a<\/td>\n\t\t <\/tr>\n\t\t \n\t\t 4a<\/td>\n\t\t (\\(\\pm\\)2a,a)<\/td> \n\t\t (2at, a\\(t^2\\))<\/td>\n\t\t y + a<\/td>\n\t\t <\/tr>\n\t\t \n\t\t 4a<\/td>\n\t\t (\\(\\pm\\)2a,-a)<\/td> \n\t\t (2at, -a\\(t^2\\))<\/td>\n\t\t y – a<\/td>\n\t\t <\/tr>\n\t\t \n\t\t 4a<\/td>\n\t\t (h+a, k\\(\\pm\\)2a)<\/td> \n\t\t (h+a\\(t^2\\), k+2at)<\/td>\n\t\t x – h + a<\/td>\n\t\t <\/tr>\n\t\t \n\t\t 4b<\/td>\n\t\t (p\\(\\pm\\)2a, q+a)<\/td> \n\t\t (p+2at, q+a\\(t^2\\))<\/td>\n\t\t y – q + b<\/td>\n\t\t <\/tr>\n\t\t <\/tbody><\/table>\n\n\n\n
\n\t\t The axis is y – \\(2\\over 3\\) = 0 \\(\\implies\\) y = \\(2\\over 3\\)
\n\t\t The directrix is x + a – h = 0 \\(\\implies\\) x + \\(61\\over 16\\) + \\(4\\over 9\\) \\(\\implies\\) x = \\(-613\\over 144\\)
\n\t\t The focus is (h+a, k) \\(\\implies\\) (\\(-485\\over 144\\), \\(2\\over 3\\))
\n\t\t Length of the latus rectum = 4a = \\(16\\over 9\\)
\n\t\t The tangent at the vertex is x – h = 0 \\(\\implies\\) x = \\(-61\\over 16\\)
<\/p>\n\n\n
\nRelated Questions<\/h3>\n