Arc Length: Measure the length of a circle arc

					PHP5
This class calculates the arc of three points on a circle. Call the class with -help argv[1]
On the command line:
		php -check-f arcLength.php 0 14 73.5 9 96 0					[arc] => 98.554522503617


		Usage:
		a) ligne de commande: php -check-f arcLength.php 0 14 73.5 9 96 0 4 >si y 1=y3=0 augmenter l'ordonnée de [ex:4]
		b) arcLength.php 0 14 73.5 9 96 0  4 >si y 1=y3=0 augmenter l'ordonnée de [ex:4]
		c) si y 1=y3=0 augmenter l'ordonnée de [ex:4] est facultatif.
				.
				.
				.(0,14)
				.	. .
				.		.   .
				.			.    .
				.				.      .   (75.5, 9)
				.					.   .  .
				.					  .     .
				.				     . .    .
				.			   	  .   .   .
				.		  (73.12,9).     . 
				.					 ...      . .
				.	 		.		  .     .    ..
				. .				  .           .(96,0)
				...................................
				(0,0)										(97.02,0)

		php -check-f arcLength.php 0  0  73.12  9  97.02  0  14  [arc] => 98.705349301392
		php -check-f arcLength.php 0 14 73.5 9 96 0					[arc] => 98.554522503617
		php -check-f arcLength.php 1  4  26  2  51  0				[arc] => 51.629657987267


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