Essential Formulas and Geometry Basics
Trigonometry is your best friend for solving triangle problems. Remember SOH CAH TOA: Sin = Opposite/Hypotenuse, Cos = Adjacent/Hypotenuse, and Tan = Opposite/Adjacent. These ratios only work with right-angled triangles, so check your triangle type first.
For any triangle, you've got two powerful rules. The sine rule (a/sin A = b/sin B = c/sin C) helps when you know two angles and one side, or two sides and a non-included angle. The cosine rule (a² = b² + c² - 2bc cos A) is perfect when you know three sides or two sides with the included angle.
Area calculations are straightforward once you know the right formula. Triangles can be calculated as ½ × base × height, or use ½ab sin C when you know two sides and the included angle. For quadrilaterals, remember that interior angles always add up to 360°, whilst exterior angles of any polygon sum to 360°.
Quick tip: Always sketch the problem - it helps you identify which formula to use and reduces calculation errors.
