Identify the given sides and angles
Determine the type of triangle
Use the Pythagorean theorem for right triangles: a² + b² = c²
Use the Law of Sines when an angle and its opposite side are known
Use the Law of Cosines when two sides and the included angle are known
Use triangle angle sum: angles add up to 180°
Solve the equation for the missing length
Check that the result is reasonable for the triangle type