Parametric Equations and Calculus
If a smooth curve C is given by the equations x f t and y g t ,
dy
then the slope of C at the point x, y is given by
dy dt
dx dx
where
dx
dt
0,
dt
d dy
d y d dy dt dx
2
and the second derivative is given by dx .
dx 2 dx dx
dt
Ex. 1 (Noncalculator)
dy d2 y
Given the parametric equations x 2 t and y 3t 2t , find
2
and .
dx dx 2
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Ex. 2 (Noncalculator)
Given the parametric equations x 4cost and y 3sint , write an equation of the tangent line to the
3
curve at the point where t .
4
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Ex 3 (Noncalculator)
Find all points of horizontal and vertical tangency given the parametric equations
x t 2 t, y t 2 3t 5.
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Ex. 4 (Noncalculator)
Set up an integral expression for the arc length of the curve given by the parametric
equations x t 2 1, y 4t 3 1, 0 t 1. Do not evaluate.
CALCULUS BC
WORKSHEET ON PARAMETRICS AND CALCULUS
Work these on notebook paper. Do not use your calculator.
dy d2 y
On problems 1 – 5, find and .
dx dx 2
1. x t 2 , y t 2 6t 5
2. x t 2 1, y 2t 3 t 2
3. x t , y 3t 2 2t
4. x lnt, y t 2 t
5. x 3sint 2, y 4cost 1
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6. A curve C is defined by the parametric equations x t 2 t 1, y t 3 t 2 .
dy
(a) Find in terms of t.
dx
(b) Find an equation of the tangent line to C at the point where t = 2.
7. A curve C is defined by the parametric equations x 2cost, y 3sint .
dy
(a) Find in terms of t.
dx
(b) Find an equation of the tangent line to C at the point where t =
.
4
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On problems 8 – 10, find:
dy
(a) in terms of t.
dx
(b) all points of horizontal and vertical tangency
8. x t 5, y t 2 4t
9. x t 2 t 1, y t 3 3t
10. x 3 2cost, y 1 4sint
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On problems 11 - 12, a curve C is defined by the parametric equations given. For each problem,
write an integral expression that represents the length of the arc of the curve over the given interval.
11. x t 2 , y t 3 , 0 t 2
12. x e2t 1, y 3t 1, 2 t 2