For the Cosine Rule of any triangle ABC, the b² is equal to

1.	For the Cosine Rule of any triangle ABC, the b² is equal to
A.	a² - c² + 2ab cos A
B.	a³ + c³ - 3ab cos A
C.	a² + c² - 2ac cos B
D.	a² - c² 4bc cos A
Answer» D. a² - c² 4bc cos A

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