Relations Between Sides and Angles of a Triangle — Formula Sheet
NIOS · Class 12 · Mathematics
3 formulas from Relations Between Sides and Angles of a Triangle (NIOS Class 12 Mathematics) on one page, grouped by topic.
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Formulas and Key Relations
Standard Notation and Basic Concepts
A + B + C = 180° (or π radians) — this is used very frequently in proofs.
Key relations
The Sine Formula states that in any triangle ABC
a/sin A = b/sin B = c/sin C, where a, b, c are the sides opposite to angles A, B, C respectively.
The Cosine Formula provides three relationships
cos A = (b² + c² - a²)/(2bc), cos B = (c² + a² - b²)/(2ac), and cos C = (a² + b² - c²)/(2ab).
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