In a ∆ABC, if a = 18, b = 24, c = 30, find cos A, cos B and cos C.
Note: In any ΔABC we define ‘a’ as length of side opposite to ∠A , ‘b’ as length of side opposite to ∠B and ‘c’ as length of side opposite to ∠C .
Key point to solve the problem:
Idea of cosine formula in ΔABC
•
Cos A =
• Cos B =
• Cos C =
As we have a = 18, b = 24 and c = 30
∴ Cos A =
Cos B =
Cos C =