Calculate triangle properties, area, perimeter, and angles
• Right Triangle: 3, 4, 5
• Equilateral: 5, 5, 5
• Isosceles: 5, 5, 3
• Sum of angles always equals 180°
• Triangle inequality: sum of any two sides > third side
• Right triangle: one angle equals 90°
• Equilateral: all sides and angles equal