What is what part of the cow is tri tip?

The tri tip is a triangular-shaped cut of beef that comes from the bottom sirloin of the cow. It is a flavorful and tender cut of meat that is often used for grilling, smoking, or roasting. The tri tip is also known as a "triangle roast" or "bottom sirloin roast" and is popular in many different cuisines, particularly in California where it is commonly served as a regional specialty.