Cogito
AP Calculus BC · Chapter 1 · Lesson 1
Parametric Equations
Two functions of a third variable.
11 problems · about 25 minutes · AP Calculus BC 9.1, 9.2
Figure — use these to answer the problems
Warm Up
Straightforward practice. Get the method working first.
4 problemsdx/dt = 3, dy/dt = 15. What is dy/dx?
Answerx = 3t, y = t. What is x when t = 4?
Answerdx/dt = 4, dy/dt = 12. What is dy/dx?
Answerdx/dt = 5, dy/dt = 0. What is dy/dx?
Answer
Build It Up
The same ideas with more to keep track of.
3 problemsx = t, y = t². Eliminating t gives y = x to what power?
AnswerSelect every true statement about parametric curves.
- They may cross themselves.
- They must pass the vertical line test.
- Eliminating the parameter loses the direction.
- dy/dx is the same as dy/dt.
- Tick every box that applies.
x = t + 2, y = 3t. What is y when x = 5?
Answer
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
4 problemsdx/dt = 0 at a point. Is the tangent vertical there? 1 for yes, 0 for no.
AnswerOrder the steps for eliminating the parameter.
Write 1 to 3 in the boxes to put these in order.
- Solve one equation for t
- Substitute into the other
- Simplify to a relation in x and y
At a Moment
x = 2t, y = t². What is x when t = 3?
AnswerThe Slope
dx/dt = 2 and dy/dt = 6. What is dy/dx?
Answer