Question

Law of cosines: a2 = b2 + c2 – 2bccos(A)

Which equation correctly applies the law of cosines to solve for an unknown angle measure?

Answer 1

Answer:

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

Step-by-step explanation:

Let us suppose a ΔABC , whose interior angles are A , B and C

Let their sides are measured as

a , b and c

where a is the side opposite to ∠A and so on.

Now there exist a formula , known as Law of cosine ,which helps us to determine the value of any angle , if all the sides of the triangle is given .

This formula is described as under

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

Above formula gives to cosine of ∠A, similarly we have formula for ∠B and ∠C

$cos B= \frac{a^2+c^2-b^2}{2ac}$

$cos C= \frac{a^2+b^2-c^2}{2ab}$