If l+m+n=0, which of the following conditions must l, m and n satisfy so that the system of simultaneous linear equations x+3y-4z=l, 2x-y-z=m, x+y-2z=n has at least one ?

In a triangle ABC, AB=AC, BC=6 cm and BE and CF are the medians drawn to AC and AB respectively. If BE^CF, then find AC (in cm).

In the given figure BC = AC, angle AFD = 40° and CE = CD. The

value of angle BCE = ?