Question

A triangle has two sides measuring 16 and 21. The included angle is 116°. What is the length of the side opposite the 116° angle?

Answer 1

Answer: A. 31.5

Explanation:

Using law of cosine because it is side angle side

a=16

b=21

angle = 116

c^2=a^2+b^2-2ab cosC, let C be the angle given

c^2=(21)^2+(16)^2-2(16)(21) cos(116)

c^2=441+256-672 cos(116)

i used a ti-89 and answered the right side and got

(you can find a ti-89 simulator online, but for problems like this make sure it is in degree mode)

991.585

c^2=991.585

take square root of both sides

=31.4894, which if you round it up it would be 31.5, so the answer would be A

therefore:

a=16

b=21

c=31.5