Use the law of cosines to find the missing angle. in triangle jkl, j=3in., k=4in., and l=2.89., find mj a. 43° b. 48° c. 31° d. 84°

option B. 48°

Explanation:

1) Data:
side j: 3 in

side k: 4in
side l: 2.89 in
angle J: ?

2) Law of cosines

j² = k² + l² - 2kl cos(J)

⇒ 3² = 4² + (2.89)² - 2(4)(2.89)cos(J)

⇒ cos(J) = [16 + 8.3521 - 9] / (23.12)

⇒cos(J) = 0.66402
⇒ J = arc cosine (0.66402) ≈ 48.39°