Find the area of the curved surface area of the cone of base radius [i]r[/i] and slanted height [i]l[/i]. (Click http://ggbtu.be/m166737 to see how the curved surface area of the cone equals this sector).
Anthony C.M. Or
GeoGebra Institute of Hong Kong
中文版：[url]161402 圓錐的曲面面積[/url]
