Curriculum
General Mathematics — Second Secondary
Unit 1: Real Functions and Curve Sketching
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Unit 2: Exponents, Logarithms and Applications
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Unit 3: Limits
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Text lesson
The Cosine Rule
The Cosine Rule
Lesson summary
Lesson summary
- a2 = b2 + c2 − 2bc cos A, and similarly for the other sides.
- cos A = (b2 + c2 − a2) / (2bc).
- Use the rule when two sides and the included angle are known, or when all three sides are known.
- If A is a right angle, the rule becomes Pythagoras’ theorem.
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