Answer to Question #59537 in Other Physics for basit ali
Why three numbers of geo stationary satellite required for global coverage
You can cover the vast majority of the Earth's surface with three satellites. Theoretically only two are needed but this means that in some places the satellite is on or near the horizon which in practice doesn't work too well if at all. For this reason three are usually used which has the added advantage that the three satellites are positioned so that they may directly communicate with each other.