You need to use the Law of Cosines:
AC² = AB² + BC² - 2·AB·BC·cos(b)
Therefore, you get:
AC = √(90² + 80² - 2·90·80·cos(50)
=√5243.86
= 72.4 in
Now you can sum up all the sides in order to find the perimeter:
AB + BC + AC = 90 + 80 + 72.4 = 242.4 in
The correct answer is A) 242.4 in
Volume (cube) = side × side × side

Volume (v) =
![{a}^{3} = 8000 {ft}^{3} \\ \sqrt[3]{ {a}^{3} } = \sqrt[3]{8000 {ft}^{3} } \\ a = 20ft](https://tex.z-dn.net/?f=%20%7Ba%7D%5E%7B3%7D%20%20%3D%208000%20%7Bft%7D%5E%7B3%7D%20%20%5C%5C%20%20%5Csqrt%5B3%5D%7B%20%7Ba%7D%5E%7B3%7D%20%7D%20%20%3D%20%20%20%5Csqrt%5B3%5D%7B8000%20%7Bft%7D%5E%7B3%7D%20%7D%20%20%5C%5C%20a%20%3D%2020ft)
And you can check because 20 × 20 × 20 = 8000, bc 20 × 20 = 400, and 400 × 20 = 8000
Cosine is probably either opp/hyp or adj/hyp