Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 3 - No. 16)
In a non-right angled triangle, with sides a,b and c and the angles opposite them A, B and C, which formula represents the cosine rule correctly?
a²=b²+c²-2bc cos A
a² = b²-c²-2bc cos A
a²=b²-c²+2bc cos A
a²=b²+c²+2bc cos A
설명
This is the correct formula of the Cosine rule.