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Ch. 11 - Parametric Equations and Polar Coordinates
Hass - Thomas' Calculus 15th Edition
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11장, 문제 11.2.14

Tangent Lines to Parametrized Curves


In Exercises 1−14, find an equation for the line tangent to the curve at the point defined by the given value of t. Also, find the value of d²y/dx² at this point.


x = t + eᵗ, y = 1 − eᵗ, t = 0

검증된 단계별 안내
1
First, find the coordinates of the point on the curve at \( t = 0 \) by substituting \( t = 0 \) into the parametric equations \( x = t + e^{t} \) and \( y = 1 - e^{t} \). This gives the point \( (x_0, y_0) \).
Next, compute the derivatives \( \frac{dx}{dt} \) and \( \frac{dy}{dt} \) by differentiating each parametric equation with respect to \( t \).
Then, find the slope of the tangent line \( \frac{dy}{dx} \) at \( t = 0 \) using the chain rule for parametric curves: \( \frac{dy}{dx} = \frac{\frac{dy}{dt}}{\frac{dx}{dt}} \).
Use the point-slope form of a line to write the equation of the tangent line at the point \( (x_0, y_0) \) with slope \( \frac{dy}{dx} \): \[ y - y_0 = \left( \frac{dy}{dx} \right)(x - x_0) \].
To find the second derivative \( \frac{d^2 y}{dx^2} \) at \( t = 0 \), first compute \( \frac{d}{dt} \left( \frac{dy}{dx} \right) \), then divide by \( \frac{dx}{dt} \) using the formula: \[ \frac{d^2 y}{dx^2} = \frac{\frac{d}{dt} \left( \frac{dy}{dx} \right)}{\frac{dx}{dt}} \]. Evaluate this expression at \( t = 0 \).

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Parametric Equations and Curves

Parametric equations express the coordinates of points on a curve as functions of a parameter, usually t. Instead of y as a function of x, both x and y depend on t, allowing the description of more complex curves. Understanding how to work with these equations is essential for analyzing the curve's behavior at specific parameter values.
추천 영상:
08:02
Parameterizing Equations

Finding the Tangent Line to a Parametric Curve

The tangent line to a parametric curve at a given t is found by computing the derivatives dx/dt and dy/dt, then using dy/dx = (dy/dt)/(dx/dt) to find the slope. The point on the curve at t gives the coordinates for the tangent point. The tangent line equation uses this slope and point to describe the line touching the curve at that parameter.
추천 영상:
가이드 코스
06:49
Differentiation of Parametric Curves

Second Derivative d²y/dx² for Parametric Curves

The second derivative d²y/dx² measures the curvature of the parametric curve and is found using the formula d²y/dx² = (d/dt(dy/dx)) / (dx/dt). This requires differentiating the slope dy/dx with respect to t and dividing by dx/dt. It provides insight into the concavity and shape of the curve at the given parameter value.
추천 영상:
가이드 코스
06:40
Higher Order Derivatives of Parametric Curves