Posted by Isabel on Wednesday, February 20, 2013 at 10:21pm.
A bridge is the shape of an arc of a circle. The bridge is 8 feet tall and 36 feet wide. What is the radius of the circle that contains the bridge? Round your answer to the nearest tenth.

Geometry (immediate help and explanation)  Reiny, Wednesday, February 20, 2013 at 10:44pm
Assuming that the 36 feet wide line base is NOT a diameter, make a sketch
let the radius be x
then I see a rightangled triangle where
(x8)^2 + 18^2 = x^2
x^2  16x + 64 + 324 = x^2
16x = 388
x = 24.25

Geometry (immediate help and explanation)  Isabel, Wednesday, February 20, 2013 at 10:51pm
Thanks! But one question..um, where did you get the triangle?

Geometry (immediate help and explanation)  Reiny, Wednesday, February 20, 2013 at 10:56pm
draw a whole circle
draw a chord AB, your base , = 36
From the centre O draw a line OA , a radius
let the radius be x
so OA = x, the hypotenuse
from the centre draw a perpendicular to AB to hit AB at C
from C to the circle is 8 , so OC = x8
OCA is a right  angled triangle.
so ...
see above
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