CBSE Class 12 Math 2013 Solved Paper

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Question : 14
Total: 29
Differentiate the following function with respect to x:
(logx)π+xlogπ
Solution:  
Let y = (logx)π+xlogπ ... (1)
Now let y1 = (logx)x and yz = xlogx
⇒ y = y1+y2 ... (2)
Differentiating (2) w.r.t. x,
dy
dx
=
dy1
dx
+
dy2
dx
... (3)
Now consider y1 = (logx)π
Taking log on both sides,
log y1 = x log (log x)
Differentiating w.r.t. x, we get
1
y1
dy1
dx
= x ×
1
logx
×
1
x
+ 1 - log (log x)
dy1
dx
= y1(
1
logx
+log(logx)
)

dy1
dx
= logxπ(
1
logx
+log(logx)
)
... (4)
⇒ Now, consider y2 = (log x) (log x) = (logx)2
Differentiating w.r.t. x, we get
1
y2
dy2
dx
= 2 log x ×
1
x

dy2
dx
= y2(
2logx
x
)
= xlogx(
2logx
x
)
... (5)
Using equations (3), (4) and (5), we get:
dy
dx
= logxπ(
1
logx
+log(logx)
)
+ xlogπ(
2logx
x
)

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