58 VII. CONGRUENT LINES IN A TRIANGLE
CD, BF are equal to and perpendicular to BI, CI respectively, and their
intersection point is also on the altitude from A.
Exercise 46. We are given a right angle AOB, and two perpendicular lines
through a point P , the ﬁrst intersecting the sides of the angle in A, B, and the
second intersecting the same sides in C, D. Show that the perpendiculars from
the points D, O, C to the line OP intercept on AB segments equal to AP , P B,
respectively, but having the opposite sense.