SE-SKOLORNAS 2001 Problem 3

Show that if $b = \frac{a+c}{2}$ in the triangle $ABC$ , then $\cos (A-C) + 4 \cos B = 3$ .

Dataset text AI-MO AoPS. Quoted with source.

Solutions

No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.