1.

Show that `xcosalpha+asin^2alpha=p`touches the parabola `y^2=4a x`if `pcosalpha+asin^2alpha=0`and that the point of contact is `(atan^2alpha,-2atanalpha)dot`

Answer» The given line is
`xcosalpha+ysinalpha=p`
`ory=-xcotalpha+p" cosec "alpha`
`:.m=-cotalphaandc=p" cosec "alpha`
Since the given line touches the parabola, we have
`c=(a)/(m)`
or cm=a
or `(pcosalpha+asin^(2)alpha=0)`
`orpcosalpha+asin^(2)alpha=0`
The point of contact is
`((a)/(cot^(2)alpha),(2a)/(cotalpha))-=(atan^(2)alpha,-2atanalpha)`


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