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A curve is defined by the parametric equations 
x(t)=-4sin(-5t) and 
y(t)=-3e^(-8t). Find 
(dy)/(dx).
Answer:

A curve is defined by the parametric equations x(t)=4sin(5t) x(t)=-4 \sin (-5 t) and y(t)=3e8t y(t)=-3 e^{-8 t} . Find dydx \frac{d y}{d x} .\newlineAnswer:

Full solution

Q. A curve is defined by the parametric equations x(t)=4sin(5t) x(t)=-4 \sin (-5 t) and y(t)=3e8t y(t)=-3 e^{-8 t} . Find dydx \frac{d y}{d x} .\newlineAnswer:
  1. Find dxdt\frac{dx}{dt}: To find dydx\frac{dy}{dx} for parametric equations, we need to find dydt\frac{dy}{dt} and dxdt\frac{dx}{dt} separately and then divide dydt\frac{dy}{dt} by dxdt\frac{dx}{dt}.
  2. Find dydt\frac{dy}{dt}: First, we find dxdt\frac{dx}{dt}. The derivative of x(t)=4sin(5t)x(t) = -4\sin(-5t) with respect to tt is dxdt=4×5×cos(5t)=20cos(5t)\frac{dx}{dt} = -4 \times -5 \times \cos(-5t) = 20\cos(-5t), since the derivative of sin(u)\sin(u) with respect to uu is cos(u)\cos(u) and we apply the chain rule for the inner function 5t-5t.
  3. Calculate dydx\frac{dy}{dx}: Next, we find dydt\frac{dy}{dt}. The derivative of y(t)=3e8ty(t) = -3e^{-8t} with respect to tt is dydt=3×8×e8t=24e8t\frac{dy}{dt} = -3 \times -8 \times e^{-8t} = 24e^{-8t}, since the derivative of eue^u with respect to uu is eue^u and we apply the chain rule for the inner function 8t-8t.
  4. Simplify dydx\frac{dy}{dx}: Now we have dxdt=20cos(5t)\frac{dx}{dt} = 20\cos(-5t) and dydt=24e8t\frac{dy}{dt} = 24e^{-8t}. To find dydx\frac{dy}{dx}, we divide dydt\frac{dy}{dt} by dxdt\frac{dx}{dt}: dydx=dydtdxdt=24e8t20cos(5t)\frac{dy}{dx} = \frac{\frac{dy}{dt}}{\frac{dx}{dt}} = \frac{24e^{-8t}}{20\cos(-5t)}.
  5. Simplify dydx\frac{dy}{dx}: Now we have dxdt=20cos(5t)\frac{dx}{dt} = 20\cos(-5t) and dydt=24e8t\frac{dy}{dt} = 24e^{-8t}. To find dydx\frac{dy}{dx}, we divide dydt\frac{dy}{dt} by dxdt\frac{dx}{dt}: dydx=dydtdxdt=24e8t20cos(5t)\frac{dy}{dx} = \frac{\frac{dy}{dt}}{\frac{dx}{dt}} = \frac{24e^{-8t}}{20\cos(-5t)}.Simplify the expression for dydx\frac{dy}{dx}: dydx=2420e8tcos(5t)=65e8tcos(5t)\frac{dy}{dx} = \frac{24}{20} \cdot \frac{e^{-8t}}{\cos(-5t)} = \frac{6}{5} \cdot \frac{e^{-8t}}{\cos(-5t)}.

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