At what domain points does the function appear to be
a. differentiable?
b. continuous but not differentiable?
c. neither continuous nor differentiable?
Answer：
Besides telling how fast an object is moving, its velocity tells the direction of motion. When the object is moving forward (s increasing), the velocity is positive; when the body is moving backward (s decreasing), the velocity is negative.
The rate at which a body’s velocity changes is the body’s acceleration. The acceleration measures how quickly the body picks up or loses speed. A sudden change in acceleration is called a jerk. When a ride in a car or a bus is jerky, it is not that the accelerations involved are necessarily large but that the changes in acceleration are abrupt.
If the equations x = f (t), y = g (t) define y as a twice-differentiable function of x, then at any point where dx/dt 0,
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