Balbharti 12th Maharashtra State Board Maths Solutions Book Pdf Chapter 1 Differentiation Ex 1.5 Questions and Answers.
12th Maths Part 2 Differentiation Exercise 1.5 Questions And Answers Maharashtra Board
Question 1.
Find the second order derivatives of the following:
(i) 2x
5
– 4x
3
– \(\frac{2}{x^{2}}\) – 9
Solution:
Let y = 2x
5
– 4x
3
– \(\frac{2}{x^{2}}\) – 9
(ii) e
2x
. tan x
Solution:
Let y = e
2x
. tan x
(iii) e
4x
. cos 5x
Solution:
Let y = e
4x
. cos 5x
(iv) x
3
. log x
Solution:
Let y = x
3
. log x
(v) log(log x)
Solution:
Let y = log(log x)
(vi) x
x
Solution:
y = x
x
log y = log x
x
= x log x
Differentiating both sides w.r.t. x, we get
Question 2.
Find \(\frac{d^{2} y}{d x^{2}}\) of the following:
(i) x = a(θ – sin θ), y = a (1 – cos θ)
Solution:
x = a(θ – sin θ), y = a (1 – cos θ)
Differentiating x and y w.r.t. θ, we get
\(\frac{d x}{d \theta}=a \frac{d}{d \theta}(\theta-\sin \theta)\) = a(1 – cos θ) …….(1)
(ii) x = 2at
2
, y = 4at
Solution:
x = 2at
2
, y = 4at
Differentiating x and y w.r.t. t, we get
(iii) x = sin θ, y = sin
3
θ at θ = \(\frac{\pi}{2}\)
Solution:
x = sin θ, y = sin
3
θ
Differentiating x and y w.r.t. θ, we get,
(iv) x = a cos θ, y = b sin θ at θ = \(\frac{\pi}{4}\)
Solution:
x = a cos θ, y = b sin θ
Differentiating x and y w.r.t. θ, we get
Question 3.
(i) If x = at
2
and y = 2at, then show that \(x y \frac{d^{2} y}{d x^{2}}+a=0\)
Solution:
x = at
2
, y = 2at ………(1)
Differentiating x and y w.r.t. t, we get
(ii) If y = \(e^{m \tan ^{-1} x}\), show that \(\left(1+x^{2}\right) \frac{d^{2} y}{d x^{2}}+(2 x-m) \frac{d y}{d x}=0\)
Solution:
y = \(e^{m \tan ^{-1} x}\) ……..(1)
(iii) If x = cos t, y = e
mt
, show that \(\left(1-x^{2}\right) \frac{d^{2} y}{d x^{2}}-x \frac{d y}{d x}-m^{2} y=0\)
Solution:
x = cos t, y = e
mt
(iv) If y = x + tan x, show that \(\cos ^{2} x \cdot \frac{d^{2} y}{d x^{2}}-2 y+2 x=0\)
Solution:
y = x + tan x
(v) If y = e
ax
. sin (bx), show that y
2
– 2ay
1
+ (a
2
+ b
2
)y = 0.
Solution:
y = e
ax
. sin (bx) ………(1)
(vi) If \(\sec ^{-1}\left(\frac{7 x^{3}-5 y^{3}}{7 x^{3}+5 y^{3}}\right)=m\), show that \(\frac{d^{2} y}{d x^{2}}=0\)
Solution:
(vii) If 2y = \(\sqrt{x+1}+\sqrt{x-1}\), show that 4(x
2
– 1)y
2
+ 4xy
1
– y = 0.
Solution:
2y = \(\sqrt{x+1}+\sqrt{x-1}\) …… (1)
Differentiating both sides w.r.t. x, we get
(viii) If y = \(\log \left(x+\sqrt{x^{2}+a^{2}}\right)^{m}\), show that \(\left(x^{2}+a^{2}\right) \frac{d^{2} y}{d x^{2}}+x \frac{d y}{d x}=0\)
Solution:
y = \(\log \left(x+\sqrt{x^{2}+a^{2}}\right)^{m}\) = \(m \log \left(x+\sqrt{x^{2}+a^{2}}\right)\)
(ix) If y = sin(m cos
-1
x), then show that \(\left(1-x^{2}\right) \frac{d^{2} y}{d x^{2}}-x \frac{d y}{d x}+m^{2} y=0\)
Solution:
y = sin(m cos
-1
x)
sin
-1
y = m cos
-1
x
Differentiating both sides w.r.t. x, we get
(x) If y = log(log 2x), show that xy
2
+ y
1
(1 + xy
1
) = 0.
Solution:
y = log(log 2x)
(xi) If x
2
+ 6xy + y
2
= 10, show that \(\frac{d^{2} y}{d x^{2}}=\frac{80}{(3 x+y)^{3}}\)
Solution:
x
2
+ 6xy + y
2
= 10 …… (1)
Differentiating both sides w.r.t. x, we get
(xii) If x = a sin t – b cos t, y = a cos t + b sin t, Show that \(\frac{d^{2} y}{d x^{2}}=-\frac{x^{2}+y^{2}}{y^{3}}\)
Solution:
x = a sin t – b cos t, y = a cos t + b sin t
Differentiating x and y w.r.t. t, we get
Question 4.
Find the nth derivative of the following:
(i) (ax + b)
m
Solution:
Let y = (ax + b)
m
(ii) \(\frac{1}{x}\)
Solution:
Let y = \(\frac{1}{x}\)
(iii) e
ax+b
Solution:
Let y = e
ax+b
(iv) a
px+q
Solution:
Let y = a
px+q
(v) log(ax + b)
Solution:
Let y = log(ax + b)
Then \(\frac{d y}{d x}=\frac{d}{d x}[\log (a x+b)]\)
(vi) cos x
Solution:
Let y = cos x
(vii) sin(ax + b)
Solution:
Let y = sin(ax + b)
(viii) cos(3 – 2x)
Solution:
(ix) log(2x + 3)
Solution:
(x) \(\frac{1}{3 x-5}\)
Solution:
Let y = \(\frac{1}{3 x-5}\)
(xi) y = e
ax
. cos (bx + c)
Solution:
y = e
ax
. cos (bx + c)
(xii) y = e
8x
. cos (6x + 7)
Solution: