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Find the partial derivative of f(x,y) with respect to y.

Mathematics

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Answer

2e2π2e^{2\pi}

Step-by-step solution

2 steps
  1. Find the partial derivative of f(x,y)f(x,y) with respect to yy.

    The given function is f(x,y)=e2ycos⁡(xy)f(x,y) = e^{2y} \cos(xy).
    We use the product rule ∂∂y(uv)=∂u∂yv+u∂v∂y\frac{\partial}{\partial y}(uv) = \frac{\partial u}{\partial y}v + u\frac{\partial v}{\partial y}.
    Let u=e2yu = e^{2y} and v=cos⁡(xy)v = \cos(xy).

    First, find ∂u∂y\frac{\partial u}{\partial y}:

    ∂∂y(e2y)=e2y⋅∂∂y(2y)=2e2y\frac{\partial}{\partial y}(e^{2y}) = e^{2y} \cdot \frac{\partial}{\partial y}(2y) = 2e^{2y}

    Next, find ∂v∂y\frac{\partial v}{\partial y}:

    ∂∂y(cos⁡(xy))=−sin⁡(xy)⋅∂∂y(xy)=−sin⁡(xy)⋅x=−xsin⁡(xy)\frac{\partial}{\partial y}(\cos(xy)) = -\sin(xy) \cdot \frac{\partial}{\partial y}(xy) = -\sin(xy) \cdot x = -x\sin(xy)

    Now, apply the product rule:

    fy(x,y)=(2e2y)cos⁡(xy)+e2y(−xsin⁡(xy))f_y(x,y) = (2e^{2y})\cos(xy) + e^{2y}(-x\sin(xy)) fy(x,y)=2e2ycos⁡(xy)−xe2ysin⁡(xy)f_y(x,y) = 2e^{2y}\cos(xy) - xe^{2y}\sin(xy)

    Factor out e2ye^{2y}:

    fy(x,y)=e2y(2cos⁡(xy)−xsin⁡(xy))f_y(x,y) = e^{2y}(2\cos(xy) - x\sin(xy))
  2. Evaluate fy(x,y)f_y(x,y) at the point (0,π)(0, \pi).

    Substitute x=0x=0 and y=πy=\pi into the expression for fy(x,y)f_y(x,y):

    fy(0,π)=e2(π)(2cos⁡(0⋅π)−0⋅sin⁡(0⋅π))f_y(0, \pi) = e^{2(\pi)}(2\cos(0 \cdot \pi) - 0 \cdot \sin(0 \cdot \pi)) fy(0,π)=e2π(2cos⁡(0)−0⋅sin⁡(0))f_y(0, \pi) = e^{2\pi}(2\cos(0) - 0 \cdot \sin(0))

    Since cos⁡(0)=1\cos(0) = 1 and sin⁡(0)=0\sin(0) = 0:

    fy(0,π)=e2π(2(1)−0(0))f_y(0, \pi) = e^{2\pi}(2(1) - 0(0)) fy(0,π)=e2π(2−0)f_y(0, \pi) = e^{2\pi}(2 - 0) fy(0,π)=2e2πf_y(0, \pi) = 2e^{2\pi}

    The final answer is 2e2π2e^{2\pi}.

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