Exercise 11.4
Question 1
निम्नलिखित फलनों को x के सापेक्ष अवकलित करें।
[Differentiate the following functions w.r.t x](i) e^{x^{3}}
Sol :
y=e^{x^{3}}
Taking log both sides
logy=loge^{x^{3}}
[\because \log _{e} m^{n}=n \cdot \log _{e} m ]
\log y=x^{3} \cdot \log e
[∵ loge=1]
log y=x3
Differentiating w.r.t.x
\frac{1}{y} \times \frac{d y}{d x}=3x^2
\frac{d y}{d x}=3 x^{2} \cdot y
\frac{dy}{dx}=3 x^{2} \cdot e^{x^{3}}
(ii) e^{-x}
Sol :
Let y=e^{-x}
Taking log both sides
log y=log e-x
log y=-x log e
log y= -x
Differentiating w.r.t.x
\frac{1}{y} \times \frac{d y}{dx}=-1
\frac{d y}{dx}=-y
-y=-e-x
(iii) e^{\cos x}
Sol :
Let y=e^{\cos x}
Taking log both sides
log y=log ecos x
log y=cos x. log e
log y=cos x
Differentiating w.r.t.x
\frac{1}{y} \times \frac{dy}{dx}=-\sin x
\frac{d y}{d x}=-\sin x \cdot y
\frac{dy}{d x}=-\sin x \cdot e^{\log x}
(iv) sin(tan-1 ex)
Sol :
Let y=sin(tan-1 ex)
Differentiating w.r.t.x
\frac{dy}{dx}=\cos \left(\tan ^{-1} e^{x}\right) \times \frac{1}{1+\left(e^{x}\right)^{2}} \times e^{x}
=\frac{e^{x}}{1+e^{2} x} \cdot \cos \left(\tan ^{-1} e^{x}\right)
(v) \sqrt{e^{\sqrt{x}}}, x>0
Sol :
Let y=\sqrt{e^{\sqrt{x}}}
Differentiating w.r.t.x
\frac{d y}{d x}=\frac{1}{2 \sqrt{e^{\sqrt{x}}}} \times e^{\sqrt x} \times \frac{1}{2 \sqrt{x}}
=\frac{e^{\sqrt{x}}}{4 \sqrt{x} \cdot \sqrt{e^{\sqrt{x}}}}
(vi) a^{x^{2}}
Sol :
y=a^{x^{2}}
Differentiating w.r.t.x
\frac{d y}{d x}=a^{x^{2}} \cdot \log a \times 2 x
=2 x a^{x^{2}} \cdot \log _{a}
(vii) \frac{e^{x} \tan x+1}{\tan x}
Sol :
Let y=\frac{e^{x} \tan x+1}{\tan x}
y=\frac{e^{x} \tan x}{\tan x}+\frac{1}{\tan x}
y=ex+cotx
Differentiating w.r.t.x
\frac{dy}{d x}=e^{x}-\operatorname{cosec}^{2} x
Question 2
निम्नलिखित फलनों को x के सापेक्ष अवकलित करें।
(i) \tan ^{-1}(\log x)
Sol :
Let y=\tan ^{-1}(\log x)
Differentiating w.r.t.x
\frac{d y}{d x}=\frac{1}{1+(\log x)^{2}} \times \frac{1}{x}
=\frac{1}{x\left[1+\left(\log {x}\right)^{2}\right]}
(ii) cos(sin(log x))
Sol :
Let y=cos(sin(log x))
Differentiating w.r.t.x
\frac{d y}{d x}=-\sin (\sin (\log x)) \cdot \cos (\log x) \times \frac{1}{x}
=-\dfrac{1}{x} \cos \left(\log {x}\right) \cdot \sin (\sin (\log x))
(iii) \log \left(x^{2} \sqrt{x^{2}+1}\right)
Sol :
Let y=\log \left(x^{2} \sqrt{x^{2}+1}\right)
y=\log x^{2}+\log \sqrt{x^{2}+1}
Differentiating w.r.t.x
\frac{d y}{dx}=2 \times \frac{1}{x}+\frac{1}{2} \times \frac{1}{x^{2}+1} \times 2x
=\frac{2\left(x^{2}+1\right)+x^{2}}{x\left(x^{2}+1\right)}
=\frac{2x^{2}+2+x^{2}}{x\left(x^{2}+1\right)}
=\frac{3 x^{2}+2}{x\left(x^{2}+1\right)}
(iv) \log \left(\frac{\sqrt{x^{2}+a^{2}}+x}{\sqrt{x^{2}+a^{2}-x}}\right)
Sol :
Let y=\log \left(\frac{\sqrt{x^{2}+a^{2}}+x}{\sqrt{x^{2}+a^{2}-x}}\right)
y=\log (\sqrt{x^{2}+a^{2}}+x)-\log (\sqrt{x^{2}+a^{2}}-x)
Differentiating w.r.t.x
\frac{d y}{d x}=\frac{1}{(\sqrt{x^{2}+a^{2}}+x)} \times\left(\frac{1}{2 \sqrt{x^{2}+a^{2}}} \times 2 x+1\right)-\frac{1}{(\sqrt{x^{2}+a^{2}-x})} \times\left(\frac{1}{2 \sqrt{x^{2}+a^{2}}} \times 2x-1\right)
\frac{d y}{d x}=\frac{1}{(\sqrt{x^{2}+a^{2}+x})} \cdot\left(\frac{x+\sqrt{x^{2}+a^{2}}}{\sqrt{x^{2}+a^{2}}}\right)+\frac{1}{(x-\sqrt{x^{2}+a^{2}})}\left(\frac{x-\sqrt{x^{2}+a^{2}}}{\sqrt{x^{2}+a^{2}}}\right)
=\frac{2}{\sqrt{x^{2}+a^{2}}}
(v) \log _{3}(\log x)
Sol :
Let y=\log _{3}(\log x)
[\because \log _{n} m=\frac{\log _{e} m}{\log _{e} n}]
y=\frac{\log (\log x)}{\log 3}
y=\frac{1}{\log 3} \cdot \log (\log x)
Differentiating w.r.t.x
\frac{d y}{d x}=\frac{1}{\log 3} \cdot \frac{1}{\log x} \times \frac{1}{x}
=\frac{1}{\log 3 \cdot x \log x}
(vi) \sin \left(e^{x} \log x\right)
Sol :
Let y=\sin \left(e^{x} \log x\right)
Differentiating w.r.t.x
\frac{d y}{d x}=\cos \left(e^{x} \log x\right)\left[e^{x} \log x+e^{x} \frac{1}{x}\right]=\cos \left(e^{x} \log {x}\right)\left[e^{x} \log{x}+\frac{e^{x}}{x}\right]
Question 3
निम्नलिखित फलनों को x के सापेक्ष अवकलित करें।
(i) e^{\sqrt{x}} \log (\cos x)
Sol :
Let y=e^{\sqrt{x}} \log (\cos x)
Differentiating w.r.t.x
\frac{dy}{d x}=e^{\sqrt{x}} \frac{1}{2 \sqrt{x}} \cdot \log \left(\cos x+e^{\sqrt{x}} \cdot \frac{1}{\cos x} \times(\sin x)\right.
=\frac{e \sqrt{x}}{2 \sqrt{x}} \log (\cos x)-e^{\sqrt{2}} \tan x
\frac{dy}{d x}=e^{\sqrt{x}} \frac{1}{2 \sqrt{x}} \cdot \log \left(\cos x+e^{\sqrt{x}} \cdot \frac{1}{\cos x} \times(\sin x)\right.
=\frac{e \sqrt{x}}{2 \sqrt{x}} \log (\cos x)-e^{\sqrt{2}} \tan x
(ii) \frac{\cos x}{\log x}, x>0
Sol :Let y=\frac{\cos x}{\log x}
Differentiating w.r.t.x
\frac{d y}{d x}=\frac{-\sin x \cdot \log x-\cos x \cdot \frac{1}{x}}{(\log x)^{2}}
=\frac{\frac{-2 \sin x \log x-\cos x}{x}}{(\log x)^{2}}
=-\frac{x \sin x \log x+\cos x}{x\left(\log x\right)^{2}}
(iii) e^{\sec ^{2} x}+3 \cos ^{-1} x
Sol :
Let y=e^{\sec ^{2} x}+3 \cos ^{-1} x
\frac{d y}{d x}=e^{s e c^{2} x} \cdot 2 \sec 2 \sec x \tan x+3\left(\frac{-1}{\sqrt{1-x^{2}}}\right)
=e^{\sec ^{2} x} \cdot 2 \sec ^{2} x \tan x-\frac{3}{\sqrt{1-x^{2}}}
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