设y=y(x)y = y(x)y=y(x)是由{x=costy=t+sin2t\begin{cases}x=\cos t\\y = t+\sin2t\end{cases}{x=costy=t+sin2t确定的函数，求dydx∣t=−π2\left.\dfrac{dy}{dx}\right|_{t = -\dfrac{\pi}{2}}dxdyt=−2π.
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