Answer:
1. Formula: b * h ÷ 2
12 * 3 = 36 ÷ 2 = 18 in^2
2. Formula: b * h ÷ 2
5 * 8 = 40 ÷ 2 = 20 ft^2
I could only help on two. Hope it helps though! =)
Answer:
About 4.123
Step-by-step explanation:
The horizontal distance between the two points is 5-1 = 4 units. the vertical distance is 3-2=1 unit. Using the Pythagorean theorem, we can find that the length is:

Take into account, that in general, a cosine function of amplitude A, period T and vertical translation b, can be written as follow:

In the given case, you have:
A = 4
T = 3π/4
b = -3
By replacing you obtain:

Hence, the answer is:
f(x) = 4cos(8/3 x) - 3