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Please solve RD Sharma class 12 chapter Differentiation exercise 10.4 question 21 maths textbook solution

Answers (1)

Answer:

\frac{d y}{d x}=\frac{\sin ^{2}(a+y)}{\sin (a+y)-y \cos (a+y)}

Hint:

Use chain rule

Given:

y=x \sin (a+y)

Solution:

y=x \sin (a+y)

Differentiate the given equation w.r.t x

\frac{d y}{d x}=\frac{d(x \sin (a+y))}{d x}

\frac{d y}{d x}=x \cdot \frac{d \sin (a+y)}{d x}+\sin (a+y) \cdot \frac{d x}{d x}

\frac{d y}{d x}=x\left[\frac{d \sin (a+y)}{d(a+y)} \times \frac{d(a+y)}{d y} \times \frac{d y}{d x}\right]+\sin (a+y)                    [Using chain rule]

 

     =x\left[\cos (a+y) \times\left(\frac{d a}{d y}+\frac{d y}{d y}\right) \times \frac{d y}{d x}\right]+\sin (a+y)

     =x\left[\cos (a+y) \times(0+1) \times \frac{d y}{d x}\right]+\sin (a+y)

\frac{d y}{d x}=x \cos (a+y) \frac{d y}{d x}+\sin (a+y)

\frac{d y}{d x}-x \cos (a+y) \frac{d y}{d x}=\sin (a+y)

\frac{d y}{d x}(1-x \cos (a+y))=\sin (a+y)

\frac{d y}{d x}=\frac{\sin (a+y)}{1-x \cos (a+y)}

y=x \sin (a+y)

x=\frac{y}{\sin (a+y)}

Put x=\frac{y}{\sin (a+y)}  in the above equation

\frac{d y}{d x}=\frac{\sin (a+y)}{1-\frac{y}{\sin (a+y)} \times \cos (a+y)}

\frac{d y}{d x}=\frac{\sin (a+y)}{\left[\frac{\sin (a+y)-y \cos (a+y)}{\sin (a+y)}\right]}

\frac{d y}{d x}=\frac{\sin ^{2}(a+y)}{\sin (a+y)-y \cos (a+y)}

Thus, proved

 

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