Sophia wants to solve for the side length of b. Which equation could Sophia use to solve for the side length of b, given the

other two side lengths and the measure of their included angle?

op? = a +62-2accos

b2-a + -2abcos

b2 = a + C2 - 2accosA

b² = a² + c² - 2ac cos B

Step-by-step explanation:

The cosine rule can be use when you are given three sides of a triangle and ask to find any angle or when you are given two sides and a included angles(the angle between the two sides given) and ask to find the length of a side.

The equation Sophia can use to solve for the side length(b) of a triangle when given two length and the included angle can be expressed below. Sophia was given two sides and an included angle and was asked to find a side length b.

For sides a, b and c the cosine rule can be represented below

a² = b² + c² - 2bc cos A

b² = a² + c² - 2ac cos B

c² = a² + b² - 2ab cos C

The equation required base on your question is

b² = a² + c² - 2ac cos B

-2

7 - 9 = -2

reversed:

-2 + 9 = 7