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# Solution for Write the Angle Made by the Tangent to the Curve X = Et Cos T, Y = Et Sin T at T = π 4 with the X-axis ? - CBSE (Commerce) Class 12 - Mathematics

#### Question

Write the angle made by the tangent to the curve x = et cos t, y = et sin t at $t = \frac{\pi}{4}$ with the x-axis ?

#### Solution

$\text { Here },$

$x = e^t \cos t \text { and } y = e^t \sin t$

$\frac{dx}{dt} = e^t cos t - e^t \sin t \text { and }\frac{dy}{dt} = e^t \sin t + e^t \cos t$

$\therefore \frac{dy}{dx} = \frac{\frac{dy}{dt}}{\frac{dx}{dt}} = \frac{e^t \sin t + e^t \cos t}{e^t cos t - e^t \sin t} = \frac{\sin t + \cos t}{\cos t - \sin t}$

$\text { Now, }$

$\text { Slope of the tangent } = \left( \frac{dy}{dx} \right)_{t = \frac{\pi}{4}} =\frac{\sin \frac{\pi}{4} + \cos \frac{\pi}{4}}{\cos \frac{\pi}{4} - \sin \frac{\pi}{4}}=\frac{\frac{1}{\sqrt{2}} + \frac{1}{\sqrt{2}}}{\frac{1}{\sqrt{2}} - \frac{1}{\sqrt{2}}}=\frac{\frac{2}{\sqrt{2}}}{0}=\infty$

$\text { Let }\theta \text { be the angle made by the tangent with thex-axis.}$

$\therefore \tan\theta=\infty$

$\Rightarrow \theta = \frac{\pi}{2}$

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Solution Write the Angle Made by the Tangent to the Curve X = Et Cos T, Y = Et Sin T at T = π 4 with the X-axis ? Concept: Tangents and Normals.
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