41.
The parabolas $${y^2} = 4x$$ and $${x^2} = 4y$$ divide the square region bounded by the lines $$x = 4,\,y = 4$$ and the coordinate axes. If $${S_1},\,{S_2},\,{S_3}$$ are respectively the areas of these parts numbered from top to bottom; then $${S_1}:{S_2}:{S_3}$$ is-
Given curves $${x^2} = \frac{y}{4}$$ and $${x^2} = 9y$$ are the parabolas whose equations can be written as $$y = 4{x^2}$$ and $$y = \frac{1}{9}{x^2}.$$
Also, given $$y = 2.$$
Now, shaded portion shows the required area which is symmetric.
$$\eqalign{
& \therefore {\text{Area}} = 2\int\limits_0^2 {\left( {\sqrt {9y} - \sqrt {\frac{y}{4}} } \right)dy} \cr
& {\text{Area}} = 2\int\limits_0^2 {\left( {3\sqrt y - \sqrt {\frac{y}{2}} } \right)dy} \cr
& = 2\left[ {\frac{2}{3} \times 3.{y^{\frac{3}{2}}} - \frac{1}{2} \times \frac{2}{3}.{y^{\frac{3}{2}}}} \right]_0^2 \cr
& = 2\left[ {2{y^{\frac{3}{2}}} - \frac{1}{3}{y^{\frac{3}{2}}}} \right]_0^2 \cr
& = \left. {2 \times \frac{5}{3}{y^{\frac{3}{2}}}} \right|_0^2 \cr
& = 2.\frac{5}{3}.2\sqrt 2 \cr
& = \frac{{20\sqrt 2 }}{3} \cr} $$
43.
Let $$f\left( x \right)$$ be a continuous function in $$R$$ such that $$f\left( x \right) + f\left( y \right) = f\left( {x + y} \right).$$ If $$\int_0^3 {f\left( x \right)dx = k} $$ then $$\int_{ - 3}^3 {f\left( x \right)dx} $$ is equal to
The required area is shown by shaded portion in the figure.
The required area is $$A = \int\limits_{ - \frac{\pi }{2}}^{\frac{\pi }{2}} {\left| {\sin \,y} \right|dy = 2\int\limits_0^{\frac{\pi }{2}} {\sin \,y\,dy} = 2} $$
46.
The value of $$\int_0^{\frac{\pi }{2}} {\frac{{dx}}{{1 + {{\tan }^3}x}}} $$ is :
48.
The area bounded by the curve $$y = f\left( x \right),\,y = x$$ and the lines $$x = 1, x = t$$ is $$\left( {t + \sqrt {1 + {t^2}} } \right) - \sqrt 2 - 1\,sq.$$ unit, for all $$t > 1.$$ If $$f\left( x \right)$$ satisfying $$f\left( x \right) > x$$ for all $$x > 1,$$ then $$f\left( x \right)$$ is equal to :
It is given that, $$f\left( x \right) > x,$$ for all $$x > 1.$$ So, area bounded by $$y = f\left( x \right),\,y = x$$ and the lines $$x = 1,\,x =
t$$ is given by $$\int_1^t {\left\{ {f\left( x \right) - x} \right\}dx} $$
But this area is given equal to $$\left( {t + \sqrt {1 + {t^2}} - \sqrt 2 - 1} \right)$$ sq unit.
Therefore, $$\int_1^t {\left\{ {f\left( x \right) - x} \right\}dx = t + \sqrt {1 + {t^2}} - \sqrt 2 - 1,{\text{ for all }}t > 1} $$
On differentiating both sides w.r.t. $$t,$$ we get
$$\eqalign{
& f\left( t \right) - t = 1 + \frac{t}{{\sqrt {1 + {t^2}} }}{\text{ for all }}t > 1 \cr
& \Rightarrow f\left( t \right) = t + 1 + \frac{t}{{\sqrt {1 + {t^2}} }}{\text{ for all }}t > 1 \cr
& {\text{Hence, }}f\left( x \right) = x + 1 + \frac{x}{{\sqrt {1 + {x^2}} }}{\text{ for all }}x > 1 \cr} $$
49.
If $$f\left( x \right) = \int_0^x {\log \left( {1 + {t^2}} \right)dt} $$ then the value of $$f''\left( 1 \right)$$ is equal to :
50.
Let $$f\left( x \right)$$ be a continuous function such that $$\int_n^{n + 1} {f\left( x \right)dx = {n^3},\,n\, \in \,Z.} $$ Then the value of $$\int_{ - 3}^3 {f\left( x \right)dx} $$ is :