OK, so the graph is a parabola, with points x=0,y=0; x=6,y=-9; and x=12,y=0
Because the roots of the equation are 0 and 12, we know the formula is therefore of the form
y = ax(x - 12), for some a
So put in x = 6
-9 = 6a(-6)
9 = 36a
a = 1/4
So the parabola has a curve y = x(x-12) / 4, which can also be written y = 0.25x² - 3x
The gradient of this is dy/dx = 0.5x - 3
The key property of a parabolic dish is that it focuses radio waves travelling parallel to the y axis to a single point. So we should arrive at the same focal point no matter what point we chose to look at. So we can pick any point we like - e.g. the point x = 4, y = -8
Gradient of the parabolic mirror at x = 4 is -1
So the gradient of the normal to the mirror at x = 4 is therefore 1.
Radio waves initially travelling vertically downwards are reflected about the normal - which has a gradient of 1, so they're reflected so that they are travelling horizontally. So they arrive parallel to the y axis, and leave parallel to the x axis.
So the focal point is at y = -8, i.e. 1 metre above the back of the dish.
28)
330.0076
29)
V = l X w X h
V = 12 X 20 X 14
12 X 7 = 84
84 X 2 = 168
168 X 20 = 3360
The volume of the cooler is 3,360 in³
Answer:
the answer is 32 units.
Step-by-step explanation:
Answer:
0.80
Step-by-step explanation:
The z-score is found from the formula ...
Z = (X -μ)/σ
Z = (77 -73)/5 = 4/5 = 0.80
Jennifer's Z-score was 0.80.
