# Trigonometric Formulae

In any âˆ† ABC,*Area of a triangle*

Area of âˆ† bc sin A, where âˆ A = BAC

Area of âˆ† ac Sin B, where âˆ B = ABC

Area of âˆ† ab Sin C, where âˆ C = ACB

# Cosine Rule and Sine Rule

In any âˆ†, we have six quantities namely the three angles and the three sides. Using the following rules, we can find any of the three quantities if we are provided with the remaining three quantities.Two important points

- The side opposite to the largest angle will be the largest.
- The side opposite to the smallest angle will be the smallest.

Example

In the figure given below, AD = CD = BC. What is the value of âˆ CDB?

Solution

*x*+

*y*= 180 â€“ 96 = 84Â° (i)

*x*+

*y*= 180 (ii)

*x*= 32Â°

So, 2

*x*= 64Â°