JEE Advance - Mathematics (1978 - No. 2)
From a point $$O$$ inside a triangle $$ABC,$$ perpendiculars $$OD$$, $$OE, OF$$ are drawn to the sides $$BC, CA, AB$$ respectively. Prove that the perpendiculars from $$A, B, C$$ to the sides $$EF, FD, DE$$ are concurrent.
The perpendiculars from A, B, C to EF, FD, DE are concurrent at the orthocenter of triangle ABC.
The perpendiculars from A, B, C to EF, FD, DE are concurrent at the circumcenter of triangle ABC.
The perpendiculars from A, B, C to EF, FD, DE are concurrent at a point related to the isogonal conjugate of O with respect to triangle ABC.
The perpendiculars from A, B, C to EF, FD, DE are concurrent at the incenter of triangle ABC.
The perpendiculars from A, B, C to EF, FD, DE are concurrent at the centroid of triangle ABC.