Q 41 :    

If the integral 5250π2sin2xcos112x(1+cos52x)12dx is equal to (n2-64), then n is equal to ______ .            [2024]



(176)

Let I=5250π2sin2x·cos112x(1+cos52x)12dx

Put cosx=t2

       -sin x dx=2 t dt

I=-525102sinx·t2·t11(1+t5)12·2tdtsinx

=525×401t3·t11(1+t5)12dt

I=210001t14(1+t5)dt

Let 1+t5=k25t4dt=2k dkt4dt=2kdk5

  I=210012(k2-1)2·k·2kdk5

         =2100×2512k2(k2-1)2dk

        =420×212(k6-2k4+k2)dk

        =840[k77-2k55+k33]12

         =840[827-825+223-(17-25+13)]

          =840[222-8105]=8[222-8]=1762-64 

So, n=176



Q 42 :    

|120π30πx2sinxcosxsin4x+cos4xdx| is equal to ________ .                 [2024]



(15)

 Let I=0πx2sinxcosxsin4x+cos4xdx

=0π/2sinxcosxsin4x+cos4x(x2-(π-x)2)dx

=0π/2sinxcosx(2πx-π2)sin4x+cos4xdx

=2π0π/2xsinxcosxsin4x+cos4xdx-π20π/2sinxcosxsin4x+cos4xdx

=2π·π40π/2sinxcosxsin4x+cos4x-π20π/2sinxcosxsin4x+cos4xdx

=-π220π/2sinxcosxsin4x+cos4x=-π220π/2sinxcosx1-2sin2x+cos2xdx

=-π220π/2sin2x1+cos22xdx

Put cos2x=t   I=-π221-1-dt2(1+t2)

=-π2201dt1+t2=-π22(tan-1t)01=-π22(π4)=-π38

  |120π30πx2sinxcosxsin4x+cos4x|=120π3×π38=15



Q 43 :    

If (a,b) be the orthocentre of the triangle whose vertices are (1, 2), (2, 3) and (3, 1) and I1=abxsin(4x-x2)dx,  I2=absin(4x-x2)dx, then 36I1I2 is equal to :    [2024]

  • 66

     

  • 88

     

  • 72

     

  • 80

     

(3)

Let the vertices of the triangle are A(3,1), B(1,2) and C(2,3).

Slope of BC=3-22-1=1

Since, AD is perpendicular to BC.

Slope of AD = -1

Equation of line AD is

y-1=-1(x-3)

Since, (a,b) lies on AD.

 b-1=-1(a-3)a+b=4

Now, I1=abxsin[(4-x)x]dx

I1=ab(a+b-x)sin[(4-(a+b-x))(a+b-x)]dx

I1=4absin[(4-x)x]dx-abxsin[(4-x)x]dx

I1=4I2-I1                                 [absin[(4-x)x]dx=I2]

2I1=4I2I1I2=2           36I1I2=36×2=72

 



Q 44 :    

Let S=(-1,) and f:SR be defined as f(x)=-1x(et-1)11(2t-1)5(t-2)7(t-3)12(2t-10)61dt. Let p=Sum of squares of the values of x, where f(x) attains local maxima on S, and q= Sum of the values of x, where f(x) attains local minima on S. Then, the value of p2+2q is ____________ .    [2024]



(27)

Given, 

f(x)=-1x(et-1)11(2t-1)5(t-2)7(t-3)12(2t-10)61dt

f'(x)=(ex-1)11(2x-1)15(x-2)7(x-3)12(2x-10)61

So, x=0, x=12, x=2, x=3, x=5

 p=0+4=4

      q=12+5=112

 p2+2q=16+11=27



Q 45 :    

401(13+x2+1+x2)dx3 loge (3) is equal to :          [2025]

  • 2+2loge (1+2)

     

  • 2+2+loge (1+2)

     

  • 22loge (1+2)

     

  • 22+loge (1+2)

     

(3)

Let f(x)=13+x2+1+x2

=3+x21+x23+x21x2=3+x21+x22

  401f(x)dx=4013+x21+x22dx

=2[013+x2dx011+x2dx]

=2[x23+x2+32 loge |x+3+x2|x21+x212 loge |x+1+x2|]01

=2+3 loge 32loge (1+2)3 loge 3

=2+3 loge 32loge (1+2)32 log 3

=22loge (1+2)+32 loge 3

=22loge (1+2)+3 loge 3

  401f(x)dx3 loge 3=22loge (1+2).



Q 46 :    

Let (a, b) be the point of intersection of the curve x2=2y and the straight line y – 2x – 6 = 0 in the second quadrant. Then the integral I=ab9x21+5xdx is equal to :          [2025]

  • 21

     

  • 18

     

  • 24

     

  • 27

     

(3)

We have, x2=2y and y – 2x – 6 = 0

Substitute y = 2x + 6 in x2=2y, we get

         x2=(4x+12)

 x24x12=0  (x6)(x+2)=0

 x=6 or 2 y=18 or 2

   Intersection points are (6, 18) and (–2, 2)

Since, (a, b) is a point in second quadrant

   (a, b) = (–2, 2)

Now, I=229x21+5xdx          ... (i)

  I=229x21+5xdx=229x25x5x+1dx          ... (ii)

On adding (i) and (ii), we get

2I=229x2(5x+1)(5x+1)dx=229x2dx

=[9x33]22=3[8(8)]=48

 I=482=24.



Q 47 :    

Let the domain of the function f(x)=log2 log4 log6 (3+4xx2) be (a, b). If 0ba[x2]dx=pqrp, q, r, gcd (p, q, r) = 1, where [·] is the greatest integer function, then p + q + r is equal to          [2025]

  • 8

     

  • 11

     

  • 9

     

  • 10

     

(4)

We have, f(x)=log2 log4 log6 (3+4xx2)

  f(x) is define when log4 log6 (3+4xx2)>0

 log6 (3+4xx2)>1

3+4xx2>6

 x2+4x3>0

 x24x+3<0

 (x1)(x3)<0

 x(1,3)

   a = 1 and b = 3

Now, 02[x2]dx=01[0]dx+12[1]dx+23[2]dx+34[3]dx

                                    =0+|x|12+2|x|23+3|x|34

                                    =(21)+2(32)+3(23)

                                    =523

 p = 5, q = 2, r = 3

   p + q + r = 5 + 2 + 3 = 10.



Q 48 :    

The integral 0π8 xdx4cos2x+sin2x is equal to            [2025]

  • π2

     

  • 4π2

     

  • 3π22

     

  • 2π2

     

(4)

Let I=0π8 xdx4cos2x+sin2x          ... (i)

 I=0π8 (πx)dx4cos2(πx)+sin2(πx)

 I=0π(8π8x)dx4cos2 x+sin2 xdx          ... (ii)

Adding (i) and (ii), we get

         2I=8π0πdx4cos2x+sin2x

 2I=8π×20πsec2 x4+tan2 xdx

Put tanx=t  sec2 xdx=dt

  I=8π0dt4+t2=8π×12[tan1t2]0

=4π×π2=2π2.



Q 49 :    

The value of 11(1+|x|x)ex+(|x|x)exex+exdx is equal to          [2025]

  • 2+223

     

  • 3223

     

  • 1223

     

  • 1+223

     

(4)

Consider, I=11(1+|x|x)ex+(|x|x)exex+ex

=11ex+ex|x|x+ex|xx|ex+exdx

=11[exex+ex+|x|x(ex+ex)ex+ex]dx

=11exex+exdx+11|x|xdx=I1+I2

Now, I1=11exex+exdx          ... (i)

 I1=11exex+exdx          ... (ii)

On adding (i) and (ii), we get

 2I1=11ex+exex+exdx=111 dx=2  I1=1

and I2=11|x|xdx=10|x|xdx+01|x|xdx

 I2=102xdx+01xxdx=102xdx

Put 2x=u  dx=12du

  I2=20u(12du)=1202udu=12[u3/232]02=223

  I=I1+I2=1+223.



Q 50 :    

Let f(x)+2f(1x)=x2+5 and 2g(x)3g(12)=x, x > 0. If α=12f(x)dx, and β=12g(x)dx, then the value of 9α+β is :          [2025]

  • 0

     

  • 11

     

  • 10

     

  • 1

     

(2)

We have, f(x)+2f(1x)=x2+5          ... (i)

 f(1x)+2f(x)=1x2+5          ... (ii)

On solving (i) and (ii), we get

f(x)=23x2x23+53

So, α=12f(x)dx=12(23x2x23+53)dx

=(23xx39+5x3)12=6379=119

Also, we have 2g(x)3g(12)=x

 2g(12)3g(12)=12  g(12)=12

so, g(x)=x234

β=12g(x)dx=12(x234)dx

=(x243x4)12=3434=0

  9α+β=9(119)+0=11.