Write the locus of the end of the pendulum of the clock.

If AB and CD are two non-parallel lines then the locus of the point P equidistant from these will be—

A triangle where orthocenter, circumcentre and incentre are coincident is called—

A triangle whose orthocentre is a vertex of the triangle is called—

The mid-points of the sides BC, CA and AB of a triangle ABC are respectively D, E and F. Then prove that EF bisects AD.