Question

What is the approximate length of the missing side in the triangle below?

13.9 mi.
19.0 mi.
21.3 mi
25.4 mi

Answer 1

C: 21.3

Explanation:

b = √a2 + c2 - 2ac·cos(B) = 21.33612

Answer 2

`21.3\:\mathrm{mi}`

Explanation:

The Law of Cosines is given as the following:

`c^2=a^2+b^2-2ab\cos C`.

Plugging in given values and solving, we get:

`c^2=15^2+18^2-2\cdot 15\cdot 18\cdot \cos 80^(\circ),\\c\approx \fbox{$21.3\:\mathrm{mi}$}`