Answer:
x = 8,49 ft
y = 4,24 ft
Step-by-step explanation:
Let x be the longer side of rectangle and y the shorter
Area of rectangle = 36 ft² 36 = x* y ⇒ y =36/x
Perimeter of rectangle:
P = 2x + 2y for convinience we will write it as P = ( 2x + y ) + y
C(x,y) = 1 * ( 2x + y ) + 3* y
The cost equation as function of x is:
C(x) = 2x + 36/x + 108/x
C(x) = 2x + 144/x
Taking derivatives on both sides of the equation
C´(x) = 2 - 144/x²
C´(x) = 0 2 - 144/x² = 0 ⇒ 2x² -144 = 0 ⇒ x² = 72
x = 8,49 ft y = 36/8.49 y = 4,24 ft
How can we be sure that value will give us a minimun
We get second derivative
C´(x) = 2 - 144/x² ⇒C´´(x) = 2x (144)/ x⁴
so C´´(x) > 0
condition for a minimum
Just substitute the first equation into the second and solve for x: <span><span>32</span>x=−<span>12</span>x+4⟹2x=4⟹x=2</span><span>Now, since y = 3/2 * x, we have y = 3 and we are done.</span>
If the legs are length a and b and hyptonuse is c then
a²+b²=c²
so
if the legs are 20 and 21 and the hypotnuse is x then
20²+21²=x²
400+441=x²
841=x²
29=x
Answer:
12
Step-by-step explanation:
Given
with reference angle 45°
hypotenuse (h) = x
perpendicular (p) = 6√2
Now
with reference angle 45°
sin 45° = p / h
1 / √2 = 6√2 / x
Cross multiply ✖
6√2 * √2 = x
x = 6 * 2
x = 12
