Learn All Concepts of Chapter 2 Class 11 Relations and Function - FREE. Check - Trigonometry Class 11 - All Concepts

For triangle Δ ABC

Cosine Law is

Here

- A, B, C are vertices of Δ ABC
- a is side opposite to A i.e. BC
- b is side opposite to B i.e. AC
- c is side opposite to C i.e. AB

Let’s look at its proof

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Another way to remember cosine formula
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Cosine formula can also be remembered as