Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 4 - No. 49)
Which statement is true about the cosine rule?
It can only be used for right-angled triangles.
It is used when you know two sides and the included angle, or when you know all three sides.
It is only used to calculate angles.
It does not involve angles.
Объяснение
The cosine rule is applicable when you know two sides and the included angle, or when you know all three sides of the triangle.