Triangles are patterns formed by converging trend lines meeting at a single point, showing a narrowing trading range. There are three main types: ascending, descending, and symmetrical triangles. Triangles indicate the market's direction before a breakout and can be traded using indicators, support/resistance levels, and fibonacci retracements to place stops and take profits. While triangles often repeat and are useful patterns, some research has found "sleeping triangles" where the market moves sideways for an extended time without a clear breakout.