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

Answer 1

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.

Answer 2

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

Answer 3

is it answer A?

Answer 4

or C