Chapter 10: Problem 20
(a) \(f(x, y)=0\) is the equation of a circle. (b) \(f(x, y) \equiv x^{2}+2 y^{2}-3 x-y+2\).
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Chapter 10: Problem 20
(a) \(f(x, y)=0\) is the equation of a circle. (b) \(f(x, y) \equiv x^{2}+2 y^{2}-3 x-y+2\).
These are the key concepts you need to understand to accurately answer the question.
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A line with gradient 2 which passes through the point \((k, 0)\) will touch the parabola \(y^{2}=4 a x\) if and only if : (a) \(k>0\) (b) \(k<0\) (c) \(k=-a\) (d) \(k<-a\) (e) \(4 k=-a\).
Find the equation of the tangent to the curve \(a y^{2}=x^{3}\) at the point \(\left(a t^{2}, a t^{3}\right)\), where \(a>0\) and \(t\) is a parameter. (U of L)
Show that the point with coordinates \((2+2 \cos \theta, 2 \sin \theta)\) lies on the circle \(x^{2}+y^{2}=4 x, \quad\) and obtain the equation of the tangent to the circle at this point. The tangents at the points \(\mathrm{P}\) and \(\mathrm{Q}\) on this circle touch the circle \(x^{2}+y^{2}=1\) at the points \(\mathrm{R}\) and \(\mathrm{S}\). Find the coordinates of the point of intersection of these tangents, and obtain the equation of the circle through the points \(\mathrm{P}, \mathrm{Q}, \mathrm{R}\) and \(\mathrm{S}\). (U of \(\mathrm{L})\)
The parametric equations of a curve are \(x=\sec \theta+1, \quad y=\tan \theta-1\). Its Cartesian equation is: (a) \(y^{2}+3=x^{2}\) (b) \(x^{2}-y^{2}-2 x-2 y=1\) (c) \(x^{2}-y^{2}+2 x+2 y+1=0\) (d) \(x^{2}-y^{2}=1\) (e) \((x-1)^{2}=y^{2}\).
Show that the equation of the normal to the parabola \(y^{2}=4 a x\) at the point \(\left(a t^{2}, 2 a t\right)\) is \(y+t x=2 a t+a t^{3}\). If this normal meets the parabola again at the point \(\left(a T^{2}, 2 a T\right)\) show that $$ t^{2}+t T+2=0 $$ and deduce that \(T^{2}\) cannot be less that 8 . The line \(3 y=2 x+4 a\) meets the parabola at the points \(P\) and \(Q\). Show that the normals at \(\mathrm{P}\) and \(\mathrm{Q}\) meet on the parabola.
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