The tangent to the curve x=cos?(3−2cos?2t) , y = sin (3−2sin2 t) at t = π /4 makes with the x-axis an angle:
This questions was previously asked in
CUET Mathematics Previous Year Question Paper 2023
Explanation:
To find the angle the tangent makes with the x-axis, we start by calculating the derivatives dx/dt and dy/dt, and then find dy/dx by dividing these derivatives.
- Given:
- \(x = \cos(3 - 2\cos^2 t)\)
- \(y = \sin(3 - 2\sin^2 t)\)
- Derivatives:
- \(\frac{dx}{dt} = -\sin(3 - 2\cos^2 t) \cdot (-4\cos t \cdot \sin t)\)
- \(\frac{dy}{dt} = \cos(3 - 2\sin^2 t) \cdot (-4\sin t \cdot \cos t)\)
- At \( t = \frac{\pi}{4} \):
- \(\cos t = \sin t = \frac{\sqrt{2}}{2}\)
- \(\frac{dx}{dt} = 2\sqrt{2} \sin(1)\)
- \(\frac{dy}{dt} = -2\sqrt{2} \cos(1)\)
- Tangent slope \(\left(\frac{dy}{dx}\right) = \frac{dy/dt}{dx/dt} = -\frac{\cos(1)}{\sin(1)} = -\cot(1)\)
- Angle with x-axis is \(\tan^{-1}\left(-\frac{\cos(1)}{\sin(1)}\right) = \pi - 1\)
- Compare this with options:
- Option 1: \(0\)
- Option 2: \(\frac{\pi}{4}\)
- Option 3: \(\frac{\pi}{6}\)
- Option 4: \(\pi - 1 \approx \frac{\pi}{3}\)
- Correct Answer: Option 4 - \(\pi/3\)
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