To cut installed tile, use an angle grinder or wet saw with a diamond blade. For straight cuts, secure the tile and mark the cut line. For angled or curved cuts, use a guide or template. Wear safety gear and secure the tile firmly. Wet cutting minimizes dust, but dry cutting is faster. Score and snap is suitable for thin tiles. For miters, use a jig or hand saw. Protect surfaces from debris. Cutting installed tile requires caution and precision to avoid damaging the surrounding tiles or the substrate.