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.
Answer: B
Step-by-step explanation:
A best describes the quality of symmetry, not specifically rotational symmetry.
C applies to that of A.
D applies to flipping an image across an axis.
B specifically outlines the symmetry of an object when rotated, thus B would be the most precise answer.
Answer:
no
Step-by-step explanation:
there is 12 inches in a foot
there are 3 feet in a yard
3 x 12 = 36 in in a yard
36 x 5 1/2 is 198
198 is greater than 192
Answer:
17.000
Step-by-step explanation:
You round up because 7 is closest to 10
Hope this helps :)
Answer:
1=5
2=1
3= 4
4=3
5=6
6=5
Step-by-step explanation:
