posted by Christine on .
if A (2, -1) and B (4,7) are endpoints of a diameter of a circle, what is the area of the circle?
Plot the two points and join 'em with a line. Now plot another point C (4, -1). And then simply run a line from B down to the new point and another one from A as well. Now u get a triangle don't u?
The height of BC will be 8cm and 2cm of that of point AC. Use pythagoras theorom to find the diameter, which is line AB. You should get 8.24
This is the length of the diameter n for finding the area u need to know the radius. So divide 8.24 by 2, which will give u 4.12
Area = r^2 times pi
Square 4.12 n u get 17
Hence the answer 17pi :)