InterviewSolution
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Let P be a point in first quadrant on parabola y^(2) = 2x whose focal distance is 5. If PF is perpendicular to SP (S is focus) which intersect x axis at point F, then the length of SF is : |
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Answer» 5 `because"FOCAL distance = 5"` `THEREFORE""a+at^(2)=(1)/(2)(1+t^(2))=5` `rArr""t=3` (in first quadrant) `rArr"P is "((9)/(2), 3)` `m_("SP")=(3-0)/((9)/(2)-(1)/(2))=(3)/(4)` `tan theta=(3)/(4)` From figure `cos theta=(5)/(SF)` `(4)/(5)=(5)/(SF) rArr SF=(25)/(4)` |
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