Cogito
AP Calculus BC · Chapter 1 · Lesson 2
Calculus of Parametric Curves
Slope and speed without eliminating t.
12 problems · about 22 minutes · CHA-3.G, CHA-6.A
Figure — use these to answer the problems
- Point(2, 4)
- Slope of the tangent4
Warm Up
Straightforward practice. Get the method working first.
5 problemsdy/dt = 18 and dx/dt = 6. What is dy/dx?
AnswerWhat is the common error when finding the second derivative?
- Forgetting to divide by dx/dt a second time.
- Getting the sign wrong.
dy/dt = 10, dx/dt = 5. What is dy/dx?
Answerdx/dt = 6, dy/dt = 8. What is the speed?
Answerx = t², so dx/dt = 2t. What is dx/dt at t = 5?
Answer
Build It Up
The same ideas with more to keep track of.
3 problemsy = t³, so dy/dt = 3t². What is dy/dt at t = 2?
Answerdx/dt = 0 and dy/dt = 5. Is the tangent vertical or horizontal? 1 vertical, 2 horizontal.
Answerdx/dt = 5 and dy/dt = 0. Vertical or horizontal? 1 or 2?
Answer
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
4 problemsPut the process for the second derivative in order.
Write 1 to 4 in the boxes to put these in order.
- Compute dy/dx as the ratio of the two rates.
- Differentiate that expression with respect to t.
- Divide the result by dx/dt again.
- Simplify to get the second derivative.
dx/dt = 5 and dy/dt = 12. What is the speed?
AnswerThe Slope
dy/dt = 12 and dx/dt = 4. What is dy/dx?
AnswerThe Speed
dx/dt = 3 and dy/dt = 4. What is the speed?
Answer