Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 3 - No. 46)
In the context of the cosine rule, what do you need to know to use it?
Two sides and the included angle
Three sides
Three angles
Two angles and the included side
Paliwanag
The cosine rule can be used when you know either two sides and the included angle, or all three sides of a triangle.