A parabolic microphone used on the sidelines of a professional football game uses a reflective dish 20 in. and 5 in. deep. How far from the bottom of the dish should the microphone be placed?
4 in.
4.6 in.
4.8 in.
5 in.
I'm really sorry this is the only answer I need could someone help?
6 answers
Update guys, it's 5 :)
20 inches what? Diameter at 5 inches from vertex?
then vertex at (0,0)
focus at (a,0)
rim at (5,10)
y^2 = 4 a x
100 = 4 a(5) = 20 a
a = 5 inches from vertex
then vertex at (0,0)
focus at (a,0)
rim at (5,10)
y^2 = 4 a x
100 = 4 a(5) = 20 a
a = 5 inches from vertex
um, thanks
unit 6 lesson 5
B
A
D
A
C
B
A
D
A
C
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Conic Sections Test Part 1:
1: 2 sqrt 13
2: have to type this one sorry D:
3: center: (0,-3); r= sqrt 5
4: (x+3)^2 + (y-2)^2=9
5: (x-4)^2 + (y+3)^2=4
6: (x-3)^2 / 16 + (y-1)^2 / 4=1
7: (x+4)^2 / 9 + (y+1)^2 / 49=1,(-4-1±2 sqrt 10)
8: this one too :(
9: 152.00 million km
10: x^2 / 3 + (y+5)^2 / 12 =1
11: (y-3)^2= -2(x-1)
12: focus: (4,3); directrix: x=6
13: 5 in
14: this is a graph question use mathway to graph it :D
15: (y+3)^2 / 25 - (x-1)^2 / 15 =1
16: y= sqrt 7 / 4 x+4 and y= - sqrt 7 / 4 x+4 (not the one in parentheses)
i'm not sure if they'll change up numbers but i got 100% so gl :D!!
1: 2 sqrt 13
2: have to type this one sorry D:
3: center: (0,-3); r= sqrt 5
4: (x+3)^2 + (y-2)^2=9
5: (x-4)^2 + (y+3)^2=4
6: (x-3)^2 / 16 + (y-1)^2 / 4=1
7: (x+4)^2 / 9 + (y+1)^2 / 49=1,(-4-1±2 sqrt 10)
8: this one too :(
9: 152.00 million km
10: x^2 / 3 + (y+5)^2 / 12 =1
11: (y-3)^2= -2(x-1)
12: focus: (4,3); directrix: x=6
13: 5 in
14: this is a graph question use mathway to graph it :D
15: (y+3)^2 / 25 - (x-1)^2 / 15 =1
16: y= sqrt 7 / 4 x+4 and y= - sqrt 7 / 4 x+4 (not the one in parentheses)
i'm not sure if they'll change up numbers but i got 100% so gl :D!!
18 answers