Question

In triangle ABC, a = 9, c = 5, and B = 120°. Find b2.

Answer 1

(D)
`b^2=151`

Explanation:

Given: In triangle ABC, a=9, c=5 and ∠B=120°.

To find: The value of
`b^2`.

solution: It is given that In triangle ABC, a=9, c=5 and ∠B=120°.

Now, using the law of cosines, we get

`b^2=a^2+c^2-2(a)(c)cosB`

Substituting the given values, we get

`b^2=9^2+5^2-2(9)(5)cosB`

`b^2=81+25-90((-1)/(2))`

`b^2=81+25+45`

`b^2=151`

which is the required value of
`b^2`.

Therefore, option D is correct.