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Your Notes
Homework
Example 3 Solve a multi-step problem
Lamp The diagram shows the hyperbolic cross section
of a lamp. Write an equation for the cross section of the
lamp. The lamp is 10 inches high. How wide is the base?
Solution
1. From the diagram, a 5 2
and b 5 4 .
Because the transverse axis
is horizontal , an equation
for the cross section of
the lamp
is x2 y2
} 2 } 5 1,
22 42 or x2
}
4
Checkpoint Complete the following exercise.
3. Write an equation for the hyperbolic cross section of
the lamp in Example 3 if the vertices are at (63, 0)
and the foci are at (65, 0). If the lamp is 15 inches
high, how wide is the base?
x2
}
9
y2
2 } 5 1
16
12.75 in.
2 y2
}
16
5 1.
(−2, 0)
Copyright © Holt McDougal. All rights reserved. Lesson 9.5 Algebra 2 Notetaking Guide 247
(0, 4)
(0, −4)
2. Find the x-coordinate at the lamp’s bottom edge.
Because the lamp is 10 inches tall, substitute
y 5 5 into the equation and solve.
x2
}
4
2 52
}
16
5 1
x 2 5 10.25
x ø 3.20
So, the lamp has a width of 2x or
2( 3.20 ) 5 6.40 inches.
y
(2, 0)
x