Which of the following is a form of the law of cosines?
A) a^2=b^2+c^2+2bc*cos A
B) a^2=b^2-c^2+2bc*cos A
C) b=a^2+c^2-2ac*cos B
D) b^2=a^2+c^2-2ac*cos B

Question

Which of the following is a form of the law of cosines?
A) a^2=b^2+c^2+2bc*cos A
B) a^2=b^2-c^2+2bc*cos A
C) b=a^2+c^2-2ac*cos B
D) b^2=a^2+c^2-2ac*cos B

usukidoll · Answer

Law of cosines looks like this

$$cosA = \frac{b^2+c^2-a^2}{2bc}$$
$$cosB = \frac{a^2+c^2-b^2}{2ac}$$
$$cosC=\frac{a^2+b^2-c^2}{2ab}$$

to have $$a^2 $$
or $$b^2$$ by itself 
we have to manipulate this a bit.

usukidoll · Answer

forgot the $$c^2 $$ case , but based on the choices you're given, I don't think you need it.

anonymous · Answer

is it answer A?

anonymous · Answer

or C