Question

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

Answer 1

Answer:

(D) $b^2=151$

Step-by-step 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

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

$b^2=81+25-90(\frac{-1}{2})$

$b^2=81+25+45$

$b^2=151$

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

Therefore, option D is correct.