Answer: D) QR^2 = 20^2 + 27^2 – 2(20)(27) ⋅ cos 99°
Explanation:
since you have the lengths of two sides and their included angle, you can use the law of cosines to solve for the missing side. let a, b, and c be the side lengths, and A be side a's respective opposite angle:
the law of cosines states that
a^2 = b^2 + c^2 - 2bc ∙ cosA
hope this helped!