The area of the triangle formed by the coordinate axes and tangent at vertex to the parabola whose focus is...
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The area of the triangle formed by the coordinate axes and tangent at vertex to the parabola whose focus is $(3,4)$ and tangents at $x=0$ and $y=0$ is?
I know how to do this, assume an equation for parabola with axis as $y=4/3 x$ and do all the procedure. But, this isn't how it is really to be solved. There's a sleek way which I cannot find.
conic-sections
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add a comment |
$begingroup$
The area of the triangle formed by the coordinate axes and tangent at vertex to the parabola whose focus is $(3,4)$ and tangents at $x=0$ and $y=0$ is?
I know how to do this, assume an equation for parabola with axis as $y=4/3 x$ and do all the procedure. But, this isn't how it is really to be solved. There's a sleek way which I cannot find.
conic-sections
$endgroup$
$begingroup$
This question is not well posed. There exist an infinite number of parabolas with focus at (3, 4). More information is needed. And "y= 4/3x" is NOT a parabola. A parabola with vertical line of symmetry can be written as $y= a(x- h)^2+ k$ and has focus $left(h, k+ frac{1}{4a}right)$. Saying that the focus is at (3, 4) means h= 3 and $k+ frac{1}{4a}= 4$ so $k= 4-frac{1}{4a}$. A parabola of the form $y= a(x- 3)^2+ 4- frac{1}{4a}$, for any a, has focus (3, 4).
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– user247327
Jan 3 at 12:19
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@user247327 No, the parabola has x=y=0 as tangents. Also, $y=4/3x$ is axis of the parabola.
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– Ice Inkberry
Jan 3 at 12:21
1
$begingroup$
How do you know that the parabola’s axis passes through the origin as you claim with that equation of the axis?
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– amd
Jan 3 at 21:46
add a comment |
$begingroup$
The area of the triangle formed by the coordinate axes and tangent at vertex to the parabola whose focus is $(3,4)$ and tangents at $x=0$ and $y=0$ is?
I know how to do this, assume an equation for parabola with axis as $y=4/3 x$ and do all the procedure. But, this isn't how it is really to be solved. There's a sleek way which I cannot find.
conic-sections
$endgroup$
The area of the triangle formed by the coordinate axes and tangent at vertex to the parabola whose focus is $(3,4)$ and tangents at $x=0$ and $y=0$ is?
I know how to do this, assume an equation for parabola with axis as $y=4/3 x$ and do all the procedure. But, this isn't how it is really to be solved. There's a sleek way which I cannot find.
conic-sections
conic-sections
asked Jan 3 at 12:13


Ice InkberryIce Inkberry
336112
336112
$begingroup$
This question is not well posed. There exist an infinite number of parabolas with focus at (3, 4). More information is needed. And "y= 4/3x" is NOT a parabola. A parabola with vertical line of symmetry can be written as $y= a(x- h)^2+ k$ and has focus $left(h, k+ frac{1}{4a}right)$. Saying that the focus is at (3, 4) means h= 3 and $k+ frac{1}{4a}= 4$ so $k= 4-frac{1}{4a}$. A parabola of the form $y= a(x- 3)^2+ 4- frac{1}{4a}$, for any a, has focus (3, 4).
$endgroup$
– user247327
Jan 3 at 12:19
$begingroup$
@user247327 No, the parabola has x=y=0 as tangents. Also, $y=4/3x$ is axis of the parabola.
$endgroup$
– Ice Inkberry
Jan 3 at 12:21
1
$begingroup$
How do you know that the parabola’s axis passes through the origin as you claim with that equation of the axis?
$endgroup$
– amd
Jan 3 at 21:46
add a comment |
$begingroup$
This question is not well posed. There exist an infinite number of parabolas with focus at (3, 4). More information is needed. And "y= 4/3x" is NOT a parabola. A parabola with vertical line of symmetry can be written as $y= a(x- h)^2+ k$ and has focus $left(h, k+ frac{1}{4a}right)$. Saying that the focus is at (3, 4) means h= 3 and $k+ frac{1}{4a}= 4$ so $k= 4-frac{1}{4a}$. A parabola of the form $y= a(x- 3)^2+ 4- frac{1}{4a}$, for any a, has focus (3, 4).
$endgroup$
– user247327
Jan 3 at 12:19
$begingroup$
@user247327 No, the parabola has x=y=0 as tangents. Also, $y=4/3x$ is axis of the parabola.
$endgroup$
– Ice Inkberry
Jan 3 at 12:21
1
$begingroup$
How do you know that the parabola’s axis passes through the origin as you claim with that equation of the axis?
$endgroup$
– amd
Jan 3 at 21:46
$begingroup$
This question is not well posed. There exist an infinite number of parabolas with focus at (3, 4). More information is needed. And "y= 4/3x" is NOT a parabola. A parabola with vertical line of symmetry can be written as $y= a(x- h)^2+ k$ and has focus $left(h, k+ frac{1}{4a}right)$. Saying that the focus is at (3, 4) means h= 3 and $k+ frac{1}{4a}= 4$ so $k= 4-frac{1}{4a}$. A parabola of the form $y= a(x- 3)^2+ 4- frac{1}{4a}$, for any a, has focus (3, 4).
$endgroup$
– user247327
Jan 3 at 12:19
$begingroup$
This question is not well posed. There exist an infinite number of parabolas with focus at (3, 4). More information is needed. And "y= 4/3x" is NOT a parabola. A parabola with vertical line of symmetry can be written as $y= a(x- h)^2+ k$ and has focus $left(h, k+ frac{1}{4a}right)$. Saying that the focus is at (3, 4) means h= 3 and $k+ frac{1}{4a}= 4$ so $k= 4-frac{1}{4a}$. A parabola of the form $y= a(x- 3)^2+ 4- frac{1}{4a}$, for any a, has focus (3, 4).
$endgroup$
– user247327
Jan 3 at 12:19
$begingroup$
@user247327 No, the parabola has x=y=0 as tangents. Also, $y=4/3x$ is axis of the parabola.
$endgroup$
– Ice Inkberry
Jan 3 at 12:21
$begingroup$
@user247327 No, the parabola has x=y=0 as tangents. Also, $y=4/3x$ is axis of the parabola.
$endgroup$
– Ice Inkberry
Jan 3 at 12:21
1
1
$begingroup$
How do you know that the parabola’s axis passes through the origin as you claim with that equation of the axis?
$endgroup$
– amd
Jan 3 at 21:46
$begingroup$
How do you know that the parabola’s axis passes through the origin as you claim with that equation of the axis?
$endgroup$
– amd
Jan 3 at 21:46
add a comment |
1 Answer
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A nice property of the parabola states that: the perpendicular from the focus to any tangent intersects it, and the tangent through the vertex, at the same point.
Hence the tangent at the vertex intersects the axes at $(3,0)$ and $(0,4)$.
$endgroup$
add a comment |
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$begingroup$
A nice property of the parabola states that: the perpendicular from the focus to any tangent intersects it, and the tangent through the vertex, at the same point.
Hence the tangent at the vertex intersects the axes at $(3,0)$ and $(0,4)$.
$endgroup$
add a comment |
$begingroup$
A nice property of the parabola states that: the perpendicular from the focus to any tangent intersects it, and the tangent through the vertex, at the same point.
Hence the tangent at the vertex intersects the axes at $(3,0)$ and $(0,4)$.
$endgroup$
add a comment |
$begingroup$
A nice property of the parabola states that: the perpendicular from the focus to any tangent intersects it, and the tangent through the vertex, at the same point.
Hence the tangent at the vertex intersects the axes at $(3,0)$ and $(0,4)$.
$endgroup$
A nice property of the parabola states that: the perpendicular from the focus to any tangent intersects it, and the tangent through the vertex, at the same point.
Hence the tangent at the vertex intersects the axes at $(3,0)$ and $(0,4)$.
edited Jan 3 at 21:54
answered Jan 3 at 16:57


AretinoAretino
22.9k21443
22.9k21443
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$begingroup$
This question is not well posed. There exist an infinite number of parabolas with focus at (3, 4). More information is needed. And "y= 4/3x" is NOT a parabola. A parabola with vertical line of symmetry can be written as $y= a(x- h)^2+ k$ and has focus $left(h, k+ frac{1}{4a}right)$. Saying that the focus is at (3, 4) means h= 3 and $k+ frac{1}{4a}= 4$ so $k= 4-frac{1}{4a}$. A parabola of the form $y= a(x- 3)^2+ 4- frac{1}{4a}$, for any a, has focus (3, 4).
$endgroup$
– user247327
Jan 3 at 12:19
$begingroup$
@user247327 No, the parabola has x=y=0 as tangents. Also, $y=4/3x$ is axis of the parabola.
$endgroup$
– Ice Inkberry
Jan 3 at 12:21
1
$begingroup$
How do you know that the parabola’s axis passes through the origin as you claim with that equation of the axis?
$endgroup$
– amd
Jan 3 at 21:46