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The differentiable functions 
x and 
y are related by the following equation:

sin(x)+cos(y)=sqrt2
Also, 
(dx)/(dt)=5.
Find 
(dy)/(dt) when 
y=(pi)/(4) and 
0 < x < (pi)/(2).

The differentiable functions x x and y y are related by the following equation:\newlinesin(x)+cos(y)=2 \sin (x)+\cos (y)=\sqrt{2} \newlineAlso, dxdt=5 \frac{d x}{d t}=5 .\newlineFind dydt \frac{d y}{d t} when y=π4 y=\frac{\pi}{4} and \( 0

Full solution

Q. The differentiable functions x x and y y are related by the following equation:\newlinesin(x)+cos(y)=2 \sin (x)+\cos (y)=\sqrt{2} \newlineAlso, dxdt=5 \frac{d x}{d t}=5 .\newlineFind dydt \frac{d y}{d t} when y=π4 y=\frac{\pi}{4} and 0<x<π2 0<x<\frac{\pi}{2} .
  1. Question Prompt: Question Prompt: Find dydt\frac{dy}{dt} when y=π4y=\frac{\pi}{4} and 0 < x < \frac{\pi}{2} given that sin(x)+cos(y)=2\sin(x) + \cos(y) = \sqrt{2} and dxdt=5\frac{dx}{dt}=5.
  2. Differentiate Equation: Differentiate both sides of the equation sin(x)+cos(y)=2\sin(x) + \cos(y) = \sqrt{2} with respect to tt.
    ddt(sin(x))+ddt(cos(y))=ddt(2)\frac{d}{dt}(\sin(x)) + \frac{d}{dt}(\cos(y)) = \frac{d}{dt}(\sqrt{2})
    Since 2\sqrt{2} is a constant, its derivative with respect to tt is 00.
  3. Apply Chain Rule: Apply the chain rule to differentiate sin(x)\sin(x) and cos(y)\cos(y) with respect to tt.ddt(sin(x))=cos(x)(dxdt)\frac{d}{dt}(\sin(x)) = \cos(x) \cdot \left(\frac{dx}{dt}\right) and ddt(cos(y))=sin(y)(dydt)\frac{d}{dt}(\cos(y)) = -\sin(y) \cdot \left(\frac{dy}{dt}\right)So, we have cos(x)(dxdt)sin(y)(dydt)=0\cos(x) \cdot \left(\frac{dx}{dt}\right) - \sin(y) \cdot \left(\frac{dy}{dt}\right) = 0
  4. Substitute Given Values: Substitute the given values into the differentiated equation.\newlineGiven dxdt=5\frac{dx}{dt} = 5 and y=π4y = \frac{\pi}{4}, substitute these values to find dydt\frac{dy}{dt}.\newlinecos(x)5sin(π4)dydt=0\cos(x) \cdot 5 - \sin\left(\frac{\pi}{4}\right) \cdot \frac{dy}{dt} = 0\newlineSince sin(π4)=22\sin\left(\frac{\pi}{4}\right) = \frac{\sqrt{2}}{2}, the equation becomes cos(x)5(22)dydt=0\cos(x) \cdot 5 - \left(\frac{\sqrt{2}}{2}\right) \cdot \frac{dy}{dt} = 0
  5. Solve for (dydt):</b>Solvefor$(dydt)(\frac{dy}{dt}):</b> Solve for \$(\frac{dy}{dt}).\newlineRearrange the equation to solve for (dydt)(\frac{dy}{dt}): (dydt)=cos(x)52/2(\frac{dy}{dt}) = \frac{\cos(x) \cdot 5}{\sqrt{2}/2}\newlineSince 0 < x < \frac{\pi}{2}, cos(x)\cos(x) is positive. Given sin(x)+cos(y)=2\sin(x) + \cos(y) = \sqrt{2} and y=π4y = \frac{\pi}{4}, cos(y)=22\cos(y) = \frac{\sqrt{2}}{2}, so sin(x)=222=22\sin(x) = \sqrt{2} - \frac{\sqrt{2}}{2} = \frac{\sqrt{2}}{2}. Thus, cos(x)=22\cos(x) = \frac{\sqrt{2}}{2}.
  6. Substitute cos(x)\cos(x): Substitute cos(x)=22\cos(x) = \frac{\sqrt{2}}{2} into the equation for dydt\frac{dy}{dt}.
    dydt=(22×5)/(22)\frac{dy}{dt} = \left(\frac{\sqrt{2}}{2} \times 5\right) / \left(\frac{\sqrt{2}}{2}\right)
    Simplifying gives dydt=5\frac{dy}{dt} = 5.

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