| 1. | The images show the principles of a linear and a polar planimeter.
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| 2. | A planimeter is a device which does integrals, using distance as the analog quantity.
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| 3. | The polar planimeter is restricted by design to measuring areas within limits determined by its size and geometry.
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| 4. | In 1893 Durand published a paper mathematically describing a radial planimeter for averaging values plotted in polar coordinates.
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| 5. | The pointer M at one end of the planimeter follows the contour C of the surface S to be measured.
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| 6. | When the planimeter's measuring wheel moves perpendicular to its axis, it rolls, and this movement is recorded.
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| 7. | The working of the linear planimeter may be explained by measuring the area of a rectangle ABCD ( see image ).
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| 8. | The same figure was also used in the old town plan of Quezon and was validated by using a digital planimeter.
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| 9. | Originally a radial planimeter was of academic interest only, but ten years later clock driven recording instruments started being used.
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| 10. | In 1887 Petersen had constructed another model; a planimeter which was presented to the Royal Danish Academy of Science and Letters.
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