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January 25, 2015

Posted by **EVJ** on Monday, July 18, 2011 at 9:16am.

10=

30=

50=

- Trig -
**MathMate**, Monday, July 18, 2011 at 9:42amIf it has a span of 160', then the equation of the parabola is

f(x)=ax(160-x)

where a is a constant, and x=0 and x=160 are the zeroes which correspond to points where the arch reaches ground/water.

The constant "a" can be found by the fact that f(80)=25.

Post your answer for a check if you wish.

- Trig -
**EVJ**, Monday, July 18, 2011 at 9:50am10 feet= 24.61 ft

30 feet= 21.48 ft

50 feet= 15.23 ft

- Trig -
**MathMate**, Monday, July 18, 2011 at 10:17amYes, the answers are all correct.

You have also correctly taken the origin at the centre of the span, which is logical since the question requires the height at distances from the centre.

Check that at negative distances the heights are the same.

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