Question

Which of the following equations could be solved to determine the length of QR?

O A) QR2 = 202 + 272 - cos 99°
B) QR2 = 202 + 272 - 2(20)(27)
C) cos 99 cos R
QR
20
D) QR2 = 202 + 272 - 2(20)(27) · cos 99°

Answer 1

d

Explanation:

quiz

Answer 2

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!