The derivative of a function of a single variable at a chosen input value, when it exists, is the slope of the tangent line to the graph of the function at that point.
Skookumchuck River (Wikipedia) The Skookumchuck River is a 45-mile (72 km) long river located in southwest Washington, United States. It is a tributary of the Chehalis River, which is the largest drainage basin located entirely within the state.
