$QR$ at $X$ and $PR$ at $Z.$ $OZ,$ $OX,$ $OY$ are perpendicular to the sides $PR,$ $QR,$ $PQ.$ Here $PQR$ is an isosceles triangle with sides $PQ = PR$ and also from the figure, \[\Rightarrow...
An isosceles triangle of vertical angle 2θ is inscribed in a circle of radius a. Show that the area of the triangle is maximum when θ = π/6.
$Δ ABC$ is an isosceles triangle such that $AB = AC.$ The vertical angle $BAC = 2θ$ Triangle is inscribed in the circle with center $O$ and radius $a.$ Draw $AM$ perpendicular to $BC.$ Since, $Δ...
Prove that the semi – vertical angle of the right circular cone of given volume and least curved surface is cot-1√2
As per the given question,
Show that the cone of the greatest volume which can be inscribed in a given sphere has an altitude equal to 2/3 of the diameter of the sphere.
Let the radius and height of cone be r and h respectively \[Radius\text{ }of\text{ }sphere\text{ }=\text{ }R\] \[{{R}^{2}}~=\text{ }{{r}^{2}}~+\text{ }{{\left( h\text{ }-\text{ }R \right)}^{2}}\]...
Prove that a conical tent of given capacity will require the least amount of canvas when the height is √2 times the radius of the base.
As per the given question,
A rectangle is inscribed in a semi-circle of radius r with one of its sides on diameter of semi-circle. Find the dimensions of the rectangle so that its area is maximum. Find also the area.
Let the length and breadth of rectangle $ABCD$ be $2x$ and $y$ respectively \[Radius\text{ }of\text{ }semicircle\text{ }=\text{ }r\text{ }\left( given \right)\] In triangle $OBA,$ where is the...
Show that the height of the cylinder of maximum volume that can be inscribed in a sphere of radius R is 2R/√3.Show that the height of the cylinder of maximum volume that can be inscribed in a sphere of radius R is 2R/√3.
As per the given question,
A large window has the shape of a rectangle surmounted by an equilateral triangle. If the perimeter of the window is 12 metres find the dimensions of the rectangle that will produce the largest area of the window.
Let the dimensions of the rectangle be $x$ and $y.$ Therefore, the perimeter of window \[=\text{ }x\text{ }+\text{ }y\text{ }+\text{ }x\text{ }+\text{ }x\text{ }+\text{ }y\text{ }=\text{ }12\]...
A window in the form of a rectangle is surmounted by a semi-circular opening. The total perimeter of the window is 10 m. Find the dimensions of the rectangular part of the window to admit maximum light through the whole opening.
Let the radius of semicircle, length and breadth of rectangle be $r,$ $x$ and $y$ respectively \[AE\text{ }=\text{ }r\] \[AB\text{ }=\text{ }x=2r\text{ }\left( semicircle\text{ }is\text{...
A tank with rectangular base and rectangular sides, open at the top is to be constructed so that its depth is 2 m and volume is 8 m3. If building of tank cost Rs 70 per square metre for the base and Rs 45 per square metre for sides, what is the cost of least expensive tank?
Let the length, breath and height of tank be $I, b$ and $h$ respectively. Also, assume volume of tank as $V$ \[h\text{ }=\text{ }2\text{ }m\text{ }\left( given \right)\] \[V\text{ }=\text{ }8\text{...
A rectangular sheet of tin 45 cm by 24 cm is to be made into a box without top, by cutting off squares from each corners and folding up the flaps. What should be the side of the square to be cut off so that the volume of the box is maximum possible?
Given length of rectangle sheet \[=\text{ }45\text{ }cm\] Breath of rectangle sheet \[=\text{ }24\text{ }cm\] Let the side length of each small square be $a.$ If by cutting a square from each corner...
A square piece of tin of side 18 cm is to be made into a box without top by cutting a square from each corner and folding up the flaps to form a box. What should be the side of the square to be cut off so that the volume of the box is maximum? Also, find this maximum volume
Given side length of big square is $18 cm$ Let the side length of each small square be $a.$ If by cutting a square from each corner and folding up the flaps we will get a cuboidal box with Length,...
Two sides of a triangle have lengths ‘a’ and ‘b’ and the angle between them is θ. What value of θ will maximize the area of the triangle? Find the maximum area of the triangle also.
It is given that two sides of a triangle have lengths $a$ and $b$ and the angle between them is $θ.$ Let the area of triangle be $A$
Find the largest possible area of a right angled triangle whose hypotenuse is 5 cm long.
As per the given question,
Given the sum of the perimeters of a square and a circle, show that the sum of their areas is least when one side of the square is equal to diameter of the circle.
Let us say the sum of perimeter of square and circumference of circle be $L$ Given sum of the perimeters of a square and a circle. Assuming, \[side\text{ }of\text{ }square\text{ }=\text{ }a\text{...
A wire of length 20 m is to be cut into two pieces. One of the pieces will be bent into shape of a square and the other into shape of an equilateral triangle. Where the wire should be cut so that the sum of the areas of the square and triangle is minimum?
Suppose the wire, which is to be made into a square and a triangle, is cut into two pieces of length $x$ and $y$ respectively. Then, \[x\text{ }+\text{ }y\text{ }=\text{ }20\text{ }\Rightarrow...
A wire of length 28 m is to be cut into two pieces. One of the pieces is to be made into a square and the other into a circle. What should be the lengths of the two pieces so that the combined area of the circle and the square is minimum?
Suppose the given wire, which is to be made into a square and a circle, is cut into two pieces of length $x$ and $y$ $m$ respectively. Then, \[x\text{ }+\text{ }y\text{ }=\text{ }28\text{...
A beam is supported at the two ends and is uniformly loaded. The bending moment M at a distance x from one end is given below. Find the point at which M is maximum in each case.
Solution: As per the given question,
Of all the closed cylindrical cans (right circular), which enclose a given volume of 100 cm^3, which has the minimum surface area?
Let $r$ $and$ $h$ be the radius and height of the cylinder, respectively. Then, Volume $(V)$ of the cylinder \[=\text{ }\pi {{r}^{2}}~h\] \[\to \text{ }100\text{ }=\text{ }\pi {{r}^{2}}~h\] \[\to...
Divide 15 into two parts such that the square of one multiplied with the cube of the other is minimum.
Let the given two numbers be $x$ and $y$. Then, \[x\text{ }+\text{ }y\text{ }=\text{ }15\text{ }\ldots ..\text{ }\left( 1 \right)\] \[y\text{ }=\text{ }\left( 15\text{ }-\text{ }x \right)\] Now we...
How should we choose two numbers, each greater than or equal to –2, whose sum is ½ so that the sum of the first and the cube of the second is minimum?
As per the given question, \[1\text{ }+\text{ }3{{\left( {\scriptscriptstyle 1\!/\!{ }_2}\text{ }-\text{ }a \right)}^{2}}~\left( -1 \right)\text{ }=\text{ }0\] \[1\text{ }-\text{ }3{{\left(...
Divide 64 into two parts such that the sum of the cubes of two parts is minimum.
Let the two positive numbers be $a$ and $b$ Given \[a\text{ }+\text{ }b\text{ }=\text{ }64\text{ }\ldots \text{ }\left( 1 \right)\] We have, \[{{a}^{3}}~+\text{ }{{b}^{3}}\] is minima Assume,...
Determine two positive numbers whose sum is 15 and the sum of whose squares is minimum.
Which implies $S$ is minimum when \[a\text{ }=\text{ }15/2\text{ }and\text{ }b\text{ }=\text{ }15/2.\]
Find the maximum value of 2x^3 – 24x + 107 in the interval [1, 3]. Find the maximum value of the same function in [–3, –1].
Let $f(x)=2 x^{3}-24 x+107$ $ \therefore f^{\prime}(x)=6 x^{2}-24=6\left(x^{2}-4\right) $ Now, for local maxima and local minima we have $f^{\prime}(x)=0$ $ \begin{array}{l} \Rightarrow...
Find the absolute maximum and the absolute minimum values of the following functions in the given intervals: (i) f (x) = 3×4 – 8×3 + 12×2 – 48x + 25 on [0, 3]
(ii) Solution: (i) Given function is $f(x)=3 x^{4}-8 x^{3}+12 x^{2}-48 x+25$ on $[0,3]$ On differentiating we get $ \begin{array}{l} f^{\prime}(x)=12 x^{3}-24 x^{2}+24 x-48 \\...
Find the absolute maximum and the absolute minimum values of the following functions in the given intervals: (i) f (x) = 4x – x^2/2 in [–2, 9/2] (ii) f (x) = (x – 1)^2 + 3 on [–3, 1]
(i) (ii) Given function is \[f\left( x \right)\text{ }=~{{\left( x\text{ }-\text{ }1 \right)}^{2}}~+\text{ }3\] On differentiation we get \[\Rightarrow \text{ }f'\left( x \right)~=\text{ }2\left(...
Show that log x/x has a maximum value at x = e.
As per the given question,
The function y = a log x + bx^2 + x has extreme values at x = 1 and x = 2. Find a and b.
Given \[y\text{ }=\text{ }a\text{ }log\text{ }x\text{ }+\text{ }b{{x}^{2}}~+\text{ }x\] On differentiating we get Given that extreme values exist at \[x\text{ }=\text{ }1,\text{ }2\] \[a\text{...
Find the local extremum values of the following functions: f (x) = – (x – 1)^3(x + 1)^2
Given $f(x)=-(x-1)^{3}(x+1)^{2}$ $ \begin{array}{l} f^{\prime}(x)=-3(x-1)^{2}(x+1)^{2}-2(x-1)^{3}(x+1) \\ =-(x-1)^{2}(x+1)(3 x+3+2 x-2) \\ =-(x-1)^{2}(x+1)(5 x+1) \\ f^{\prime...
Find the local extremum values of the following functions: (i) f(x) = (x – 1) (x – 2)^2
Solution: (i) $ \begin{array}{l} \text { Given } f(x)=(x-1)(x-2)^{2} \\ f(x)=(x-2)^{2}+2(x-1)(x-2) \\ =(x-2)(x-2+2 x-2) \\ =(x-2)(3 x-4) \\ f^{\prime}(x)=(3 x-4)+3(x-2) \end{array} $ For maxima and...
Find the points of local maxima or local minima and corresponding local maximum and local minimum values of each of the following functions. Also, find the points of inflection, if any: f (x) = x e^x
Given $\mathrm{f}(\mathrm{x})=\mathrm{x} \mathrm{e}^{x}$ $ \begin{array}{l} f(x)=e^{x}+x e^{i}=e^{x}(x+1) \\ f^{\prime}(x)=e^{2}(x+1)+e^{t} \\ =e^{2}(x+2) \end{array} $ For maxima and minima, $...
Find the points of local maxima or local minima and corresponding local maximum and local minimum values of each of the following functions. Also, find the points of inflection, if any: (i) f(x) = (x – 1) (x + 2)^2 (ii) f (x) = 2/x – 2/x^2, x > 0
(i) Given $f(x)=(x-1)(x+2)^{2}$ $ \begin{array}{l} \therefore \mathrm{f}(\mathrm{x})=(\mathrm{x}+2)^{2}+2(\mathrm{x}-1)(\mathrm{x}+2) \\ =(\mathrm{x}+2)(\mathrm{x}+2+2 \mathrm{x}-2) \\...
Find the points of local maxima or local minima and corresponding local maximum and local minimum values of each of the following functions. Also, find the points of inflection, if any: (i) f(x) = x^4 – 62x^2 + 120x + 9 (ii) f (x) = x^3 – 6x^2 + 9x + 15
(i) Given $f(x)=x^{4}-62 x^{2+} 120 x+9$ $ \begin{array}{l} \therefore \mathrm{f}(\mathrm{x})=4 \mathrm{x}^{\mathrm{a}}-124 x+120=4\left(\mathrm{x}^{a}-31 \mathrm{x}+30\right) \\...
Find the points of local maxima or local minima, if any, of the following functions, using the first derivative test. Also, find the local maximum or local minimum values, as the case may be: f (x) = sin 2x, 0 < x < π
Given \[f\text{ }\left( x \right)\text{ }=\text{ }sin\text{ }2x\] Differentiate w.r.t x, we get \[f'\left( x \right)\text{ }=\text{ }2\text{ }cos\text{ }2x,\text{ }0\text{ }<\text{ }x\text{...
Find the points of local maxima or local minima, if any, of the following functions, using the first derivative test. Also, find the local maximum or local minimum values, as the case may be: f (x) = x^3 – 6x^2 + 9x +15
Given, $f(x)=x^{3}-6 x^{2}+9 x+15$ Differentiate with respect to $x$, we get, $f^{\prime}(x)=3 x^{2}-12 x+9=3\left(x^{2}-4 x+3\right)$ $=3(x-3)(x-1)$ For all maxima and minima, $ \begin{array}{l}...
Find the points of local maxima or local minima, if any, of the following functions, using the first derivative test. Also, find the local maximum or local minimum values, as the case may be: f(x)=1/(x^2+2)
As per the given question, Therefore \[x\text{ }=\text{ }0,\] now for the values close to \[x\text{ }=\text{ }0,\] and to the left of \[0,\text{ }f'\left( x \right)\text{ }>\text{ }0\] Also for...
Find the points of local maxima or local minima, if any, of the following functions, using the first derivative test. Also, find the local maximum or local minimum values, as the case may be: f (x) = (x – 1) (x + 2)2
Differentiate with respect to $x$, we get, $ \begin{array}{l} f(x)=(x+2)^{2}+2(x-1)(x+2) \\ =(x+2)(x+2+2 x-2) \\ =(x+2)(3 x) \end{array} $ For all maxima and minima, $ \begin{array}{l} f(x)=0 \\...
Find the points of local maxima or local minima, if any, of the following functions, using the first derivative test. Also, find the local maximum or local minimum values, as the case may be: f (x) = x^3 (x – 1)^2
Given, $f(x)=x^{2}(x-1)^{2}$ Differentiate with respect to $x$, we get, $ \begin{array}{l} {\left x=3 x^{2}(x-1)^{2}+2 x^{2}(x-1)\right.} \\ =[x-1]\left(3 x^{2}(x-1)+2 x^{2}\right) \\ =[x-1]\left(3...
Find the points of local maxima or local minima, if any, of the following functions, using the first derivative test. Also, find the local maximum or local minimum values, as the case may be: f (x) = x^3 – 3x
Given, $f(x)=x^{2}-3 x$ Differentiate with respect to $x$ then we get, $ f(x)=3 x^{2}-3 $ $\mathrm{Now}, \mathrm{f}(x)=0$ $ 3 x^{2}=3 \Rightarrow x=\pm 1 $ Again differentiate $f(x)=3 x^{2}-3$ $...
Find the points of local maxima or local minima, if any, of the following functions, using the first derivative test. Also, find the local maximum or local minimum values, as the case may be: f (x) = (x – 5)^4
Given $f(x)=(x-5)^{4}$ Differentiate with respect to $x$ $ f(x)=4(x-5)^{2} $ For local maxima and minima $ \begin{array}{l} f(x)=0 \\ =4(x-5)^{2}=0 \\ =x-5=0 \\ x=5 \end{array} $ $f(x)$ changes from...
Find the maximum and the minimum values, if any, without using derivatives of the following functions: f (x) = |sin 4x + 3| on R
Given $f(x)=|\sin 4 x+3|$ on $R$ We know that $-1 \leq \sin 4 x \leq 1$ $ \begin{array}{l} \Rightarrow 2 \leq \sin 4 x+3 \leq 4 \\ \Rightarrow 2 \leq|\sin 4 x+3| \leq 4 \end{array} $ Hence, the...
Find the maximum and the minimum values, if any, without using derivatives of the following functions: f (x) = sin 2x + 5 on R
Given $f(x)=\sin 2 x+5$ on $R$ We know that $-1 \leq \sin 2 x \leq 1$ $ \begin{array}{l} \Rightarrow-1+5 \leq \sin 2 x+5 \leq 1+5 \\ \Rightarrow 4 \leq \sin 2 x+5 \leq 6 \end{array} $ Hence, the...
Find the maximum and the minimum values, if any, without using derivaties of the following functions: f (x) = |x + 2| on R
Given $f(x)=|x+2|$ on $R$ $\Rightarrow f(x) \geq 0$ for all $x \in R$ So, the minimum value of $f(x)$ is 0, which attains at $x=-2$ Hence, $f(x)=|x+2|$ does not have the maximum value.
Find the maximum and the minimum values, if any, without using derivatives of the following functions: f (x) = –(x – 1)^2 + 2 on R
Given $f(x)=-(x-1)^{2}+2$ It can be observed that $(x-1)^{2} \geq 0$ for every $x \in R$ Therefore, $f(x)=-(x-1)^{2}+2 \leq 2$ for every $x \in R$ The maximum value of $f$ is attained when $(x-1)=0$...
Find the maximum and the minimum values, if any, without using derivatives of the following functions: f (x) = 4x^2 – 4x + 4 on R
Given $f(x)=4 x^{2}-4 x+4$ on $R$ $=4 x^{2}-4 x+1+3$ By grouping the above equation we get, $ =(2 x-1)^{2}+3 $ Since, $(2 x-1)^{2} \geq 0$ $ \begin{array}{l} =(2 x-1)^{2}+3 \geq 3 \\ =f(x) \geq f(1...
Using binomial theorem, prove that 23n – 7n – 1 is divisible by 49, where n ∈ N.
Answer: Given, 23n – 7n – 1 23n – 7n – 1 = 8n – 7n – 1 Using binomial theorem, 8n = 7n + 1 8n = (1 + 7) n 8n = nC0 + nC1 (7)1 + nC2 (7)2 + nC3 (7)3 + nC4 (7)2 + nC5 (7)1 + … + nCn (7) n 8n = 1 + 7n...