JEE MAIN - Mathematics (2010 - No. 15)
If two tangents drawn from a point $$P$$ to the parabola $${y^2} = 4x$$ are at right angles, then the locus of $$P$$ is
$$2x+1=0$$
$$x=-1$$
$$2x-1=0$$
$$x=1$$
説明
The locus of perpendicular tangents is directrix
i.e., $$x=-1$$
i.e., $$x=-1$$