Second derivatives Find y′′ for the following functions. y=x\sin (x)

Brittney Lord

Brittney Lord

Answered question

2021-11-08

Second derivatives Find y′′ for the following functions.
y=xsin(x)

Answer & Explanation

lamanocornudaW

lamanocornudaW

Skilled2021-11-09Added 85 answers

Step 1
Here given function,
y=xsin(x)
and we have to find the second derivatives of the given function.
concept used: product rules of derivation
Rule is.
ddx[f(x)g(x)]=ddx[f(x)]g(x)+f(x)ddx[g(x)]
Here,
f(x)=x
g(x)=sin(x)
we find first derivative of given function and then find second derivative as follows.
Step 2
Rewrite the function:
d2dx2(xsin(x))
=ddx(xsin(x))
=ddx(x)sin(x)+xddxsin(x)
ddx(xsin(x))=sin(x)+xcos(x)
this is first derivative now differentiate it again to get second derivative:
ddx(sin(x)+xcos(x))
=ddx(sin(x))xcos(x)+sin(x)ddx(xcos(x))
=xcosxcosx+sinx[ddxxcosx+xddxcosx]
=xcos2x+sinx(cos(x)xsinx)
=xcos2x+sinxcosxxsin2x
=2cos(x)xsin(x)

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