First we have to find the mean (average)
mean = (564 + 1000 + 848 + 1495 + 1348) / 5 = 5255 / 5 = 1051
now we subtract the mean from every data point, then square it
564 - 1051 = -487......-487^2 = 237169
1000 - 1051 = -51......-51^2 = 2601
848 - 1051 = -203......-203^2 = 41209
1495 - 1051 = 444......444^2 = 197136
1348 - 1051 = 297......297^2 = 88209
now find the mean of the results.....but know when ur dealing with a sample instead of the whole population, u divide by 1 number less...so instead of dividing by 5, u divide by 4.
(237169 + 2601 + 41209 + 197136 + 88209) / 4 = 566324 / 4 =
141581.....this is called ur variance
now take the square root of the variance and u have ur standard deviation
sqrt (141581) = 376.272 rounds to 376.27 <==
Answer:
I think this is the answer
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:
90 degrees
Step-by-step explanation:
BCO = 66
The whole ABC is 180
So BCO and BDO = 90
Therefore BAO must = 90 degrees
