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SAT® Subject Test in Math 1 & 2

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Moderate

An Equivalent Law of Cosines

SATSTM-OQQSJY

Given the formula for the Law of Cosines, which one of the following is an equivalent equation?

$${a}^{2}={b}^{2}+{c}^{2}-2\text{bc}\cdot\text{cos}\text{ A }$$

A

$\text{cos A}=\cfrac{{b}^{2}+{c}^{2}+{a}^{2}}{2\text{bc}}$

B

$\text{cos A}=\cfrac{{b}^{2}+{c}^{2}-{a}^{2}}{2\text{bc}}$

C

$\text{cos A}=\cfrac{{a}^{2}-{b}^{2}-{c}^{2}}{2\text{bc}}$

D

$\text{cos A}=\cfrac{{b}^{2}+{c}^{2}-{a}^{2}}{2a}$

E

$\text{None of the Above}$