Use cosine law to solve the problem. See image attached.
What we're looking for is the length of side A (a side which is opposite with angle A).
This is the formula of cosine law
A² = B² + C² - 2BC cos A
Input the numbers
A² = 75² + 90² - 2(75)(90) cos 85°
A =

A =
6i^4 = 6*1 = 6
6i^3 = 6*(-i) = -6i
-2i^2 = (-2)*(-1) = 2
sqrt(-49) = 7i
So, we have: 6 - 6i + 2 + 7i = 8 + i
The answer is D
Formula for triangle perimeter is: a + b + c. In this scenario we have:
a = 3 feet 8 inches
b = 2 feet 10 inches
c = 4 feet
a + b + c =
= 3 ft + 8 in + 2 ft + 10 in + 4 ft =
= 9 ft + 18 in
We know that 1 foot is 12 inches, so we can simplify the result to this form:
10 ft + 6 in
or:
<u>10.5 feet</u>