MathDB
Obtuse triangle

Source: Canada 1970, Problem 2

May 14, 2006
trigonometry

Problem Statement

Given a triangle ABCABC with angle AA obtuse and with altitudes of length hh and kk as shown in the diagram, prove that a+hb+ka+h\ge b+k. Find under what conditions a+h=b+ka+h=b+k. [asy] size(6cm);
pair A = dir(105), C = dir(170), B = dir(10), D = foot(B, A, C), E = foot(A, B, C);
draw(A--B--C--cycle); draw(B--D--A--E);
dot(A); dot(B); dot(C); dot(D); dot(E);
label("AA", A, dir(110)); label("BB", B, B); label("CC", C, C); label("DD", D, D); label("EE", E, dir(45));
label("hh", A--E, dir(0)); label("kk", B--D, dir(45)); [/asy]