PHP algorithm exercise ten: Calculate the radius and center coordinates of a circle

In the previous article "PHP Algorithm Exercise 9: Convert all even numbers to all odd numbers" I introduced to you how to convert all even numbers to all odd numbers through PHP, so today I will continue to show you Bringing the PHP algorithm exercise series~

This article will introduce to you how to calculate the radius and center coordinates of a circle through PHP~

The specific problem descriptionis "How to write a PHP program to calculate the radius and center coordinates (x, y) of a circle formed by three given points on a plane”?

This problem is equivalent to a mathematical problem. Given three points, determine the radius and center coordinates of a circle.

Look at the picture below:

I will provide you with several formulas:

The formula for setting up a circle is as follows:

Convert the circle equation into a standard equation:

Substitute the above coefficients to solve the circle center (x, y) and radius R:

PHP implementation code is as follows:

"); printf("(%.3f %.3f) %.3f\n", $x, $y, $r);

The calculation result is:

圆的中心坐标(x,y)和半径: (1.000 1.000) 1.414

Note:

sqrt() function Returns the square root of a number.

The syntax is "sqrt(x)", which means returning the square root of x.

The parameter x represents a number. If the parameter x is a negative number, the sqrt() function returns -1.#IND. (Attachment: Before PHP 5.3.0, this function treated the array as a string Array, thus returning a string with a length of 5 and generating an E_NOTICE level error.)

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