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Derivatives & Second-Order Derivatives · Question 60 of 96

Question 60

HardOriginal question

A curve is given by x=t−1tx = t - \frac{1}{t}, y=t+1ty = t + \frac{1}{t}. What is its slope dydx\frac{dy}{dx} at t=2t = 2?

Options for question 60

Show the answer and explanation
CorrectNot quiteAnswer B

Correct answer: B

Explanation

  1. dxdt=1+1t2\frac{dx}{dt} = 1 + \frac{1}{t^{2}} and dydt=1−1t2\frac{dy}{dt} = 1 - \frac{1}{t^{2}}.

  2. dydx=dy/dtdx/dt=t2−1t2+1\frac{dy}{dx} = \frac{dy/dt}{dx/dt} = \frac{t^{2} - 1}{t^{2} + 1}.

  3. At t=2t = 2 the slope is 35\frac{3}{5}.

Worth noting

Dividing the other way round gives dxdy\frac{dx}{dy}.

Concept
Slope of a parametric curve
Typical time
120 s
Your time
—
The rule this testsParametric functions
Practise this chapter →

Ten questions from Derivatives & Second-Order Derivatives, at your own pace.

Practise this chapter →

Ten questions from Derivatives & Second-Order Derivatives, at your own pace.