Q 21 :

The integral 80∫0π4(sinθ+cosθ9+16sin2θ)dθ is equal to :          [2025]

  • 4loge3

     

  • 2loge3

     

  • 3loge4

     

  • 6loge4

     

(1)

Let I=80∫0π4(sinθ+cosθ)dθ(9+16sin2θ)

=80∫0π4(sinθ+cosθ)dθ9+16(1–1+2sinθcosθ)

=80∫0π4(sinθ+cosθ)dθ25–16(sinθ–cosθ)2

Put sinθ–cosθ=t ⇒ (cosθ+sinθ)dθ=dt

When θ=0, t=–1 and θ=π/4, t=0.



Q 22 :

Let f(x)=∫0xt(t2–9t+20)dt, 1≤x≤5. If the range of f is [α,β], then 4(α+β) equals :          [2025]

  • 253

     

  • 154

     

  • 157

     

  • 125

     

(3)

We have, f(x)=∫0xt(t2–9t+20)dt

⇒f'(x)=x3–9x2+20x=x(x–4)(x–5)

Where 1≤x≤5

On integration, we get

f(x)=x44–9x33+20x22

             =x44–3x3+10x2, where 1≤x≤5

∴  f(1)=14–3+10=294=α

         f(4)=(4)44–3(4)3+10(4)2=32=β

         f(5)=(5)44–3(5)3+10(5)2=1254

∴  4(α+β)=4(294+32)=157



Q 23 :

Let [·] denote the greatest integer function. If ∫0e3[1ex–1]dx=α–loge2, then α3 is equal to __________.          [2025]



(8)

Let f(x)=1ex–1=e1–x

f(0)=e1=2.71; f(e3)=e1–e3∈(0,1)

Let f(x)=2 ⇒ 1ex–1=2 ⇒ x=1–loge2

and f(x)=1 ⇒ x=1

∴  I=∫01–loge22dx+∫1–loge211 dx+∫1e30 dx

=2(1–loge2–0)+(1–1+loge2)+0=2–loge2

∴        α=2

Hence, α3=8.



Q 24 :

If limt→0(∫01(3x+5)tdt)1t=α5e(85)23, then α is equal to _________.          [2025]



(64)

Let L=limt→0(∫01(3x+5)tdx)1t

           =elimt→01t(∫01(3x+5)tdx–1)

           =elimt→01t[((3x+5)t+13(t+1))01–1]          [∵ 1∞ form]

            =elimt→0[8t+1–5t+1–3t–33t(t+1)]

            =elimt→0{[8·8t–5·5t–3t–(8–5)3t]·limt→0(1t+1)}

             =elimt→013[8(8t–1)t–5(5t–1)t–3tt]

              =e(8 ln(8)–5 ln(5)–3)3=e[ln(8)8/3–ln(5)5/3–ln e]

=(8)8/3(5)5/3·e ⇒ (85)23·825·1e=α5e(85)23          [Given]

On comparing, we get

∴  α=82=64.



Q 25 :

If 24∫0π4(sin|4x–π12|+[2sinx])dx=2π+α, where [·] denotes the greatest integer function, then α is equal to _________.         [2025]



(12)

Let I=24∫0π4(sin |4x–π12|+[2 sin x])dx

=24[∫0π/48[–sin (4x–π12)]dx+∫π/48π/4sin (4x–π12)dx+∫0π/6[0]dx+∫π/6π/4[1]dx]

=24[(1–cosπ12)–(–1–cosπ12)+π4–π64]

=24(12+π12)=12+2π

⇒ I=12+2π=2π+α          [Given]

On comparing, we get α=12.



Q 26 :

Let 5f(x)+4f(1x)=1x+3, x>0. Then 18∫12f(x) dx is equal to          [2023]

  • 5loge2+3    

     

  • 10loge2+6    

     

  • 5loge2-3    

     

  • 10loge2-6

     

(4)

We have, 5f(x)+4f(1x)=1x+3  ...(i) 

Replace x by 1x, we get 5f(1x)+4f(x)=x+3  ...(ii) 

Solving (i) and (ii), we get 25f(x)-16f(x)=5x+15-4x-12 

⇒ 9f(x)=5x-4x+3⇒ f(x)=19{5x-4x+3}

∴  18∫12f(x) dx=18×19∫12(5x-4x+3)dx 

=2[5logx-4x22+3x]12

=2[5log2-6+3]=10log2-6



Q 27 :

Let f(x) be a function satisfying f(x)+f(π-x)=π2,∀x∈ℝ. Then ∫0πf(x)sinx dx is equal to           [2023]

  • π2

     

  • 2π2

     

  • π22

     

  • π24

     

(1)

Let I=∫0πf(x)sinx dx  ...(i) 

⇒ I=∫0πf(π-x)sin(π-x) dx

⇒ I=∫0πf(π-x)sinx dx  ...(ii) 

Adding (i) and (ii), we get  

2I=∫0π[f(x)+f(π-x)]sinx dx 

⇒ I=π22∫0πsinx dx             (∵f(x)+f(π-x)=π2)

=π22[-cosx]0π=π22[2]=π2



Q 28 :

If I(x)=∫esin2x(cosxsin2x-sinx) dx and I(0)=1, then I(π3) is equal to             [2023]

  • -e34

     

  • e34

     

  • 12e34

     

  • -12e34

     

(3)

I(x)=∫esin2x(cosxsin2x-sinx)dx 

=∫eg(x)[f(x)g'(x)+f'(x)]dx              [where g(x)=sin2x and f(x)=cosx] 

=eg(x)f(x)+C=esin2x·cosx+C

As I(0)=1,  

∴    esin20cos(0)+C=1 ⇒C=0 ∴ I(x)=esin2xcosx 

Hence, I(π3)=esin2π3cosπ3=12e34 



Q 29 :

Let f be a continuous function satisfying ∫0t2(f(x)+x2) dx=43t3,∀t>0. Then f(π24) is equal to            [2023]

  • π(1-π316)  

     

  • -π2(1+π316)  

     

  • -π(1+π316)  

     

  • π2(1-π216)

     

(1)

Given, ∫0t2(f(x)+x2) dx=43t3,∀ t>0 

Using Leibnitz Rule, we get

[f(t2)+(t2)2]·2t=4t2⇒f(t2)+t4=2t ⇒f(t2)=2t-t4 

Put t=π2 

f((π2)2)=2π2-(π2)4=π-π416=π(1-π316)



Q 30 :

The value of the integral ∫-loge2loge2ex(loge(ex+1+e2x))dx is equal to            [2023]

  • loge(2(2+5)1+5)-52

     

  • loge(2(3-5)21+5)+52

     

  • loge((2+5)21+5)+52

     

  • loge(2(2+5)21+5)-52

     

(4)

Let I=∫-loge2loge2ex(ln(ex+1+e2x))dx 

Put ex=t⇒exdx=dt 

When x=-loge2, t=12;  when x=loge2, t=2

∴  I=∫1/22ln(t+1+t2)dt 

Applying integration by parts, we get

I=[tln(t+1+t2)]1/22-∫1/22tt+1+t2(1+2t21+t2)dt 

=2ln(2+5)-12ln(1+52)-∫1/22t1+t2dt 

=2ln(2+5)-12ln(1+52)-[1+t2]1/22 

=2ln(2+5)-12ln(1+52)-52=ln((2+5)2(5+12)12)-52
 

 



Q 31 :

If f:ℝ→ℝ be a continuous function satisfying ∫0π/2f(sin2x)sinx dx+α∫0π/4f(cos2x)cosx dx=0, then the value of α is          [2023]

  • -2

     

  • 3

     

  • -3

     

  • 2

     

(1)

I=∫0π/4f(sin2x)sinx dx+∫π/4π/2f(sin2x)sinx dx+α∫0π/4f(cos2x)cosx dx=0 

Apply ∫0af(x) dx=∫0af(a-x) dx in the first part and put  x-π4=t in the second part, we get

I=∫0π/4f(cos2x)sin(π4-x)dx+∫0π/4f(cos2t)sin(π4+t)dt+α∫0π/4f(cos2x)cosx dx=0

=∫0π/4f(cos2x)[2sinπ4·cosx+αcosx]dx=0 

(α+2)∫0π/4f(cos2x)cosx dx=0  ∴  α=-2

[∵ In (0,π4), f(cos(2x)) and cosx are not zero.]



Q 32 :

Let the function f:[0,2]→ℝ be defined as f(x)={emin{x2, x-[x]},x∈[0,1)e[x-logex],x∈[1,2) where [t] denotes the greatest integer less than or equal to t. Then the value of the integral ∫02xf(x)dx is                  [2023]

  • (e-1)(e2+12)  

     

  • 2e-12

     

  • 1+3e2

     

  • 2e-1

     

(2)

f(x)={emin{x2, x-[x]},x∈[0,1)e[x-logex],x∈[1,2)

For x∈[0,1);  min{x2, {x}}=x2 

and for x∈[1,2); [x-logex]=1 

∴ f(x)={ex2,x∈[0,1)e,x∈[1,2)

Now, ∫02xf(x)=∫01xex2 dx+∫12xedx 

=12(e-1)+12(4-1)e=2e-12



Q 33 :

∫0∞6e3x+6e2x+11ex+6dx=                  [2023]

  • loge(6427)  

     

  • loge(51281)

     

  • loge(25681)

     

  • loge(3227)

     

(4)

Put ex=t⇒ex dx=dt and on solving, we get loge(3227)

 



Q 34 :

The value of e-π4+∫0π4e-xtan50x dx∫0π4e-x(tan49x+tan51x) dx is:            [2023]

  • 51

     

  • 49

     

  • 25

     

  • 50

     

(4)

e-π/4+∫0π/4e-xtan50x dx∫0π/4e-x(tan49x+tan51x)dx

First, simplify, ∫0π/4e-xtan50xdx

=[-e-x(tanx)50]0π/4+∫0π/4e-x(50)tan49x·sec2x dx

=-e-π/4+0+50∫0π/4e-x(tanx)49(1+tan2x) dx

=-e-π/4+50∫0π/4e-x[(tanx)51+(tanx)49]dx

Now, -e-π/4+∫0π/4e-x(tanx)50dx∫0π/4e-x(tan49x+tan51x)dx

=50∫0π/4e-x(tan51x+tan49x)dx∫0π/4e-x(tan49x+tan51x)dx=50

∴  e-π/4+∫0π/4e-xtan50x dx∫0π/4e-x(tan49x+tan51x)dx=50



Q 35 :

If ∫011(5+2x-2x2)(1+e(2-4x))dx=1αloge(α+1β), α,β>0, then α4-β4 is equal to           [2023]

  • - 21

     

  • 0

     

  • 21

     

  • 19

     

(3)

Let I=∫011(5+2x-2x2)(1+e(2-4x))dx

I=∫011(5+2x(1-x))·e4x(e4x+e2) dx                  ...(i)

We know that, ∫abf(x) dx=∫abf(b+a-x)dx

∴   I=∫0115+2(1-x)·x·e4(1-x)e4(1-x)+e2 dx            ...(ii)

Adding (i) and (ii), we get

⇒2I=∫0115+2(1-x)·x[e4xe4(1-x)+e4xe2+e4xe4(1-x)+e4(1-x)·e2(e4(1-x)+e2)(e4x+e2)]dx

⇒2I=∫01dx5+2(1-x)·x=∫01dx112-2(x-12)2

=∫01dx(114-(x-12)2)

⇒I=111 ln(11+110)

∴  α=11 and β=10  ∴α4-β4=121-100=21



Q 36 :

limn→∞[11+n+12+n+13+n+…+12n] is equal to           [2023]

  • loge2  

     

  • loge(23)  

     

  • 0

     

  • loge(32)

     

(1)

limn→∞[11+n+12+n+13+n+…+12n]

=limn→∞∑r=1n1r+n=limn→∞1n∑r=1n11+rn=∫01dx1+x=ln[1+x]|01=ln2



Q 37 :

The value of the integral ∫-π4π4x+π42-cos2xdx is                 [2023]

  • π2123

     

  • π26  

     

  • π233  

     

  • π263

     

(4)

I=∫-π4π4x+π42-cos2x dx  ...(i)

Replace x by -x, we get

I=∫-π4π4-x+π42-cos2x dx  ...(ii)

Adding (i) and (ii), we get

2I=∫-π4π4π/22-cos2xdx⇒ I=π4·2∫0π4dx2-cos2xdx

⇒I=π4·2∫0π4 (1+tan2x) dx2(1+tan2x)-(1-tan2x)

=π2∫0π4 sec2x dx2(1+tan2x)-(1-tan2x)

Let tanx=t⇒sec2x dx=dt

at x=0,t=0 and x=π4,t=1

I=π2∫01dt3t2+1⇒ I=π6∫01dtt2+(13)2=π63·[tan-13t]01

⇒I=π23tan-13    I=π263



Q 38 :

∫324334489-4x2dx is equal to               [2023]

  • 2π

     

  • π6

     

  • π3

     

  • π2

     

(1)

 



Q 39 :

The minimum value of the function f(x)=∫02e|x-t| dt is                [2023]

  • 2

     

  • 2(e - 1)

     

  • 2e - 1

     

  • e(e - 1)

     

(2)

Case 1: When x<0

f(x)=∫02et-xdt=e-x(et)02=e-x(e2-1)

Case 2: When 0<x<2

f(x)=∫0xex-tdt+∫x2et-xdt ⇒f(x)=ex(-e-t)0x+e-x(et)x2

=-ex(e-x-1)+e-x(e2-ex)=-1+ex+e2e-x-1=ex+e-xe2-2

Case 3: When x≥2

f(x)=∫02e(x-t)dt=ex(-e-t)02=-ex(e-2-1)

Hence,

f(x)={e-x(e2-1),x<0 ex+e-xe2-2,0≤x<2(1-e-2)ex,x≥2

f(x) is decreasing for x<0 and increasing for x≥2.  

f(x) is also continuous.

For 0≤x≤2, f(x) is minimum at x=1.  

(Using A.M.–G.M. inequality)

Hence, the minimum value f(x)=f(1)=2(e-1)



Q 40 :

The integral 16∫12dxx3(x2+2)2 is equal to                [2023]

  • 116-loge4

     

  • 1112+loge4

     

  • 116+loge4

     

  • 1112-loge4

     

(1)

Let I=16∫12dxx3(x2+2)2=16∫121x7(1+2x2)2dx

Let 1+2x2=p ⇒ -4x3dx=dp ⇒ dxx3=-14dp

I=-4∫33/2dp4(p-1)2·p2

=-4∫33/2(p-1)2dp4p2 =-∫33/2p2+1-2pp2dp

=-∫33/2(1+1p2-2p)dp=-[p-1p-2logp]33/2

=-[{56-2loge(32)}-{83-2loge3}]

=-[2loge2-116]=116-loge22=116-loge4



Q 41 :

Let [x] denote the greatest integer ≤x. Consider the function f(x)=max{x2, 1+[x]}. Then the value of the integral ∫02f(x) dx is            [2023]

  • 5+423

     

  • 8+423

     

  • 1+523

     

  • 4+523

     

(1)

Given f(x)=max{x2,1+[x]}

So, ∫02f(x) dx=∫011 dx+∫122 dx+∫22x2 dx

               =1+2(2-1)+8-223=5+423



Q 42 :

Let f(x)=x+aπ2-4sinx+bπ2-4cosx, x∈ℝ be a function which satisfies f(x)=x+∫0π/2sin(x+y)f(y) dy. Then (a+b) is equal to        [2023]

  • -π(π+2)

     

  • -π(π-2)

     

  • -2π(π+2)

     

  • -2π(π-2)

     

(3)

f(x)=x+∫0π/2(sinxcosy+cosxsiny)f(y) dy

=x+∫0π/2((cosy f(y) dy)sinx+(siny f(y) dy)cosx)                 ...(i)

On comparing with f(x)=x+aπ2-4sinx+bπ2-4cosx

⇒aπ2-4=∫0π/2cosy f(y) dy                            ...(ii)

⇒bπ2-4=∫0π/2siny f(y) dy                               ...(iii)

Adding (ii) and (iii), we get

a+bπ2-4=∫0π/2(siny+cosy)f(y) dy                  ...(iv)

a+bπ2-4=∫0π/2(siny+cosy)f(π2-y)dy          ...(v)

Adding (iv) and (v), we get

2(a+b)π2-4=∫0π/2(siny+cosy)[π2+(a+b)π2-4(siny+cosy)]dy

=π+a+bπ2-4(π2+1) ⇒(a+b)=-2π(π+2)



Q 43 :

The value of the integral ∫1/22tan-1xxdx is equal to               [2023]

  • 12loge2

     

  • πloge2

     

  • π4loge2

     

  • π2loge2

     

(4)

We have the integral as follows  

I=∫1/22tan-1xxdx  …(1)

By substituting x=1t and dx=-1t2dt in equation (1),

I=-∫21/2tan-11t1t·1t2·dt

I=-∫21/2tan-11ttdt=∫1/22cot-1ttdt=∫1/22cot-1xxdx  …(2)

On adding equation (1) and (2), we have  

2I=∫1/22tan-1x+cot-1xxdx;   2I=π2∫1/22dxx=π2[logx]1/22

      2I=π2[loge2-loge12]=πloge2

⇒ 2I=πloge2     ∴ I=π2loge2

Hence, option (4) is the correct answer.



Q 44 :

The value of the integral ∫12(t4+1t6+1)dt is                 [2023]

  • tan-12-13tan-18+π3

     

  • tan-12+13tan-18-π3

     

  • tan-112+13tan-18-π3

     

  • tan-112-13tan-18+π3

     

(2)

Let I=∫12[t4+1t6+1]dt

=∫121t2+1dt+13∫123t2(t3)2+1dt

=[tan-1t]12+[13(tan-1t3)]12

=tan-12+13tan-18-π3



Q 45 :

If [t] denotes the greatest integer ≤t, then the value of 3(e-1)e∫12x2e[x]+[x3] dx is             [2023]

  • e8-1  

     

  • e7-1  

     

  • e9-e  

     

  • e8-e

     

(4)

Let I=3(e-1)e∫12x2e[x]+[x3] dx

Between 1 and 2, [x] = 1, so e[x]=e.

∴   I=3(e-1)∫12x2·e[x3] dx

Let x3=t⇒x2dx=dt3

I=3(e-1)3∫18e[t] dt=(e-1)∫18e[t] dt

=(e-1)[e+e2+e3+e4+e5+e6+e7]=(e-1)[e(e7-1)e-1]

⇒e(e7-1)=e8-e



Q 46 :

limn→∞3n{4+(2+1n)2+(2+2n)2+⋯+(3-1n)2} is equal to            [2023]

  • 193  

     

  • 12

     

  • 0

     

  • 19

     

(4)

We have, limn→∞3n{4+(2+1n)2+(2+2n)2+⋯+(3-1n)2}

=limn→∞3n{(2+0n)2+(2+1n)2+⋯+(2+(n-1n))2}

=limn→∞3n∑r=0n-1(2+rn)2=3∫01(2+x)2dx

Let 2+x=tdx=dt⇒3∫23t2 dt=3×[t32]23=33[27-8]=19



Q 47 :

Let α∈(0,1) and β=loge(1-α).  Let Pn(x)=x+x22+x33+…+xnn,x∈(0,1). Then the integral ∫0αt501-tdt is equal to            [2023]

  • P50(α)-β  

     

  • -(β+P50(α))  

     

  • β+P50(α)  

     

  • β-P50(α)

     

(2)

We have, Pn(x)=x+x22+x33+⋯+xnn, x∈(0,1)                       ...(i)

Let I=∫0αt501-tdt=∫0αt50+1-11-tdt=∫0α(-(1-t50)1-t+11-t)dt

=∫0α-(1+t+t2+…+t49)dt+∫0α11-tdt

=-[t+t22+t33+⋯+t5050]0α-[log(1-t)]0α

=-log(1-α)-[α+α22+α33+⋯+α5050]

=-β-P50(α)                     [∵ β=loge(1-α) and from (i)]

=-(β+P50(α))



Q 48 :

The value of ∫π/3π/2(2+3sinx)sinx(1+cosx)dx is equal to             [2023]

  • 72-3-loge3  

     

  • 103-3-loge3  

     

  • 103-3+loge3  

     

  • -2+33+loge3

     

(3)

Let I=∫π/3π/22+3sinxsinx(1+cosx)dx

=∫π/3π/22(1-cosx)sinx(1-cos2x)dx+∫π/3π/23(1+cosx)dx

=∫π/3π/22sin3xdx-∫π/3π/22cosxsin3xdx+32∫π/3π/21cos2x2dx

=2∫π/3π/2cosec2x cosec2xdx-2∫π/3π/2cotx·cosec2xdx+32[2tanx2]π/3π/2

=2∫π/3π/21+cot2x cosec2 dx-2∫π/3π/2cotx·cosec2dx+3[tanπ4-tanπ6]

Let cotx=t⇒cosec2x dx=-dt and  

For x=π2; t=0 and for x=π3; t=13

∴   I=-2∫1/301+t2 dt+2∫1/30t dt+3[1-13]

=-2[t21+t2+12loge(t+1+t2)]1/30 +[t2]1/30+(3-3)

=23+log3-13+3-3=103-3+loge3



Q 49 :

If ϕ(x)=1x∫π/4x(42sint-3ϕ'(t))dt,x>0, then ϕ'(π4) is equal to            [2023]

  • 46+π  

     

  • 86+π  

     

  • 8π  

     

  • 46-π

     

(2)

By Leibnitz rule,

ϕ'(x)=1x[(42sinx-3ϕ'(x))·1-0]-12x-3/2∫π/4x(42sint-3ϕ'(t))dt

Put x=π4, we get ϕ'(π4)=2π[4-3ϕ'(π4)]+0

⇒(1+6π)ϕ'(π4)=8π=8π×(π6+π)=86+π



Q 50 :

Let α>0. If ∫0αxx+α-xdx=16+20215, then α is equal to              [2023]

  • 2  

     

  • 22  

     

  • 4  

     

  • 2

     

(1)

After rationalising, I=∫0αxα(x+α+x)dx

=∫0α1α[(x+α)3/2-α(x+α)1/2+x3/2]dx

=1α[25(x+α)5/2-α23(x+α)3/2+25x5/2]0α

=1α(25(2α)5/2-2α3(2α)3/2+25α5/2-25α5/2+23α5/2)

=1α(27/2α5/25-25/2α5/23+23α5/2)=α3/2(27/25-25/23+23)

=α3/215(242-202+10)=α3/215(42+10)

Now, α3/215(42+10)=16+20215=22(42+10)15

⇒α3/2=22=23/2⇒α=2