Search zone

1. Write a function distance that takes four numbers that contain the coordinates of two points (x1,y1) and (x2,y2), and returns the distance between those two points.

2. Write a function circumference_area that takes the radius of a circumference and returns its area.

3. A mountain rescue team needs an application to compute the area of a given zone. Sometimes they are given two reference points to determine a circular search zone, the first one being the center and the second lying on the perimeter. Write the function compute_search_area that takes the x,y coordinates of the center and the x,y coordinates of a point on the perimeter, and returns the area of the search zone. This function will call the two functions on the preceding paragraphs.