GUATEMALA CITY - Torrential rains brought by the first tropical storm of the 2010 season pounded Central America and southern Mexico, triggering deadly landslides. The death toll stood at 15 Sunday but authorities said the number could rise.
Archimedes proved the formula for the area of a circle (A = Ï r 2, where r is the radius of the circle) and showed that the value of Ï lay between 3 + 1/7 (approximately 3.1429) and 3 + 10/71 (approximately 3.1408).
With this notation, you can now use more than one function at a time without confusing yourself or mixing up the formulas, wondering Okay, which ' y ' is this, anyway?. And the notation can be usefully explanatory:  A(r) = (pi)r2  indicates the area of a circle, while  C(r) = 2(pi)r  indicates the circumference.