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101.

If `tan((alphapi)/(4))=cot((betapi)/(4)),` thenA. `alpha +beta=0`B. `alpha+beta=2n`C. `alpha+beta+2n+1`D. `alpha+beta=2(2n+1), n inZ`

Answer» Correct Answer - D
102.

Let `alpha, beta` be such that `pi lt alph-betalt3piif sin alpha+sinbeta=-21/65and cos alpha+cos beta =-27/65,` then the value of `cos""(alpha-beta)/(2),` isA. `-(6)/(65)`B. `(3)/(sqrt130)`C. `6/65`D. `-(3)/(sqrt130)`

Answer» Correct Answer - D
We have,
`sin alpha+sinbeta=-21/65and cos alpha+cosbeta=-27/65`
`implies2sin""(alpha+beta)/(2)cos""(alpha-beta)/(2)=-21/65`
`and 2cos""(alpha+beta)/(2)cos""(alpha-beta)/(2)=-27/65`
`implies4(sin^(2)""(alpha+beta)/(2)+cos^(2)""(alpha+beta)/(2))cos^(2)""(alpha-beta)/(2)=(-(21)/(65))^(2)+(-(27)/(65))^(2)`
`implies4cos^(2)((alpha-beta)/(2))=(1170)/(65^(2))`
`implies4cos^(2)((alpha-beta)/(2))=(1170)/(4xx65^(2))`
`implies|cos""(alpha-beta)/(2)|=(sqrt(1170))/(130)`
`impliescos""(alpha-beta)/(2)=-(sqrt(1170))/(130)" "[{:(,because(pi)/(2)lt(alpha-beta)/(2)lt(3pi)/(2)),(,thereforecos""(alpha-beta)/(2)lt0):}]`
`impliescos""(alpha-beta)/(2)=-sqrt((1170)/(130xx130))=-(3)/(sqrt(130))`
103.

The number of integral triplets (a, b, c) such thet `a+b cos 2x+c sin^(2)x=0` for all x, is

Answer» Correct Answer - D
We have,
`a+bcos2x+c sin^(2)x=0` for all x
`impliesa+b+(c-2b)sin^(2)x=0` for all x
`impliesa+b=0and c-2b=0`
`impliesa=-bandc =2b`
Thus, the triplets are `(-b,b,2b), where b in R.`
Hence, there are infinitely many triplets.
104.

If A > 0, B > 0 and `A+B=pi/6`, then the minimum value of `tan A + tan B` isA. `2-sqrt3`B. `(2)/(sqrt3)`C. `sqrt3-sqrt2`D. `4-2sqrt3`

Answer» Correct Answer - D
`tan A +tan D`
`=tanA+tan((pi)/(6)-A)=tanA+(tan""(pi)/(6)-tanA)/(1+tan""(pi)/(6)tanA)`
`=tanA+(1-sqrt3tanA)/(sqrt3+tanA)=(1+tan^(2)A)/(sqrt3+tanA)=(1)/(sqrt3cos^(2)A+sinA cos A)`
`=(2)/(sqrt3(1+cos2A)+sin2A)=(2)/(sqrt3+(sqrt3cos2A+sin2A))`
`=(1)/((sqrt3)/(2)+sin(2A+(pi)/(3))`
`Now, 0ltAlt(pi)/(6)implies0lt2Alt(pi)/(3)`
`implies(pi)/(3)lt2A+(pi)/(3)lt(2pi)/(3)implies(sqrt3)/(2)ltsin(2A+(pi)/(3))le1`
`impliessqrt3lt(sqrt3)/(2)+sin(2A+(pi)/(3))le(sqrt3)/(2)+1`
`implies(2)/(2+sqrt3)le(1)/((sqrt3)/(2)+sin(2A+(pi)/(3)))lt(1)/(sqrt3)`
`implies2(2-sqrt3)le tanA+tanBlt(1)/(sqrt3)` lt
105.

If `A+B+C=0,` then the value of `sum cot (B+C-A) cot (C+A-B)` is equal to

Answer» Correct Answer - B
106.

If `a sin x+b cos(x+theta)+b cos(x-theta)=d,` then the minimum value of `|cos theta|` is equal toA. `(1)/(2|b|)sqrt(d^(2)-a^(2))`B. `(1)/(2|a|)sqrt(d^(2)-a^(2))`C. `(1)/(|d|)sqrt(d^(2)-a^(2))`D. none of these

Answer» Correct Answer - A
We have,
`a sinx+bcos(x+theta)+b cos(x-theta)=d` for some real x
`impliesa sinx+2bcos x costheta=d`
`implies|d|lesqrt(a^(2)+4b^(2)cos^(2)theta)`
`impliesd^(2)lea^(2)+4b^(2)cos^(2)theta`
`implies(d^(2)-a^(2))/(4b^(2))lecos^(2)thetaimpliescosthetage""(1)/(2|b|)sqrt(d^(2)-a^(2))`
Hence, the minimum value of `cos thetais (1)/(1|b|)sqrt(d^(2)-a^(2))`
107.

If x,y,z are variables and `3tan x+4tany+5tanz=20,` then the minimum value of `tan^(2)x+tan^(2)y+tan^(2)z,` isA. 10B. 15C. 8D. 12

Answer» Correct Answer - C
`Let veca=3hati+4hatj+5hatk`
and, `hatb=(tanx)hati+(tany)hatk+(tanz)hatk.` Then,
`(veca,vecb)^(2)le|veca|^(2)|vecb|^(2)`
`implies(3tanx+4tany+5tanz)^(2)`
`" "le(9+16+25)(tan^(2)x+tan^(2)y+tan^(2)z)`
`implies(20)^(2)le50(tan^(2)x+tan^(2)y+tan^(2)z)`
`impliestan^(2)x+tan^(2)y+tan^(2)zge8`
108.

In `(0,pi//2)tan^(m)x+cot^(m)x` attainsA. a minimum value which is independent of mB. a minimum value which is a function of mC. the minimum value of 2D. the minimum value at the some point indiependent of m.

Answer» Correct Answer - B
109.

Find the Value of `tan 82 1/2^@`A. `sqrt2+sqrt3+sqrt4+sqrt6`B. `(sqrt3+sqrt2)(sqrt2-1)`C. `-(sqrt3+sqrt2)(sqrt2+1)`D. none of these

Answer» Correct Answer - A
110.

if `y=cos^2theta+sec^2theta` thenA. `y=0`B. `y le2`C. `y ge-2`D. `y ne2`

Answer» Correct Answer - D
111.

If `sin2theta=cos3theta` and `theta` is an acute angle , then `sintheta` is equal toA. `(sqrt5-1)/(4)`B. `-((sqrt5-1)/(4))`C. `(sqrt5+1)/(4)`D. `(-sqrt5-1)/(4)`

Answer» Correct Answer - A
112.

If `A+B=pi/3 and cos A+cos B=1,` then which of the following is/are true ?A. `cos(A-B)=1/3`B. `|cosA-cosB|=sqrt(2/3)`C. `cos(A-B)=-2/3`D. `|cosA-cosB|=(1)/(2sqrt3)`

Answer» Correct Answer - B::C
We have,
`cosA+cos B=1`
`implies2 cos ""(A+B)/(2)cos""(A-B)/(2)=1`
`impliescos""(A-B)/(2)=(1)/(sqrt(3))" "[becauseA+B=(pi)/(3)]`
`implies2 cos^(2)""((A-B)/(2))-1=2/3-1impliescos(A-B)=-1/3`
Now, `|cosA-cosB|`
`=|2sin((A+B)/(2))sin((B-A)/(2))|`
`=|2sin""(pi)/(6)sin((A-B)/(2))|`
`= |sin((A-B)/(2))|=sqrt(1-cos^(2)((A-B)/(2)))=sqrt(1-(1)/(3))=sqrt((2)/(3))`
So, option (b) is also true,
113.

Which of the following statements about `tan10^(@)` is true?A. It is a rational numberB. It is an inrrational number less than 2C. It is an irrational number greater than 2D. It is greater than 2

Answer» Correct Answer - B::C
Since tan `theta` is an increasing function on `(0,pi//2)`
`thereforetan10^(@)lttan15^(@)=2-sqrt3lt2.`
Thus option (c ) is true.
Now, `tan30^(@)=(3 tan10^(@)-tan^(3)10^(@))/(1-3tan^(2)10^(@))`
If `tan 10^(@)` is a trational number, then `(3tan10^(@)-tan^(3)10^(@))/(1-3tan^(2)10^(@))` must be a rational number, which is not true,
Hence, `tan10^(@)` is an irrational number.
114.

The value of `sec 40^(@)+sec 80^(@)+sec 160^(@)` will beA. 4B. `-4`C. 6D. 8

Answer» Correct Answer - C
We find that
`cos40^(@)+cos80^(@)cos160^(@)`
`2cos60^(@)cos20^(@)-cos20^(@)=0`
`cos40^(@)cos80^(@)+cos80^(@)cos160^(@)+160^(@)cos40^(@)`
`=1/2[2cos80^(@)cos40^(@)+2cos160^(@)cos80^(@)+2cos160^(@)cos40^(@)]`
`=1/2[cos120^(@)+cos40^(@)+cos240^(@)+cos80^(@)+cos200^(@)+cos120^(@)]`
`=1/2(-1/2+2cos40^(@)-1/2+cos80^(@)-cos20^(@)""1/2)`
`=1/2(-(3)/(2)+cos60^(@)cos20^(@)-cos20^(@))=-3/4` and, `cos40^(@)cos80^(@)cos160^(@)=(sin(2^(3)xx40^(@)))/(2^(3)sin40^(@))=1/8(sin320^(@))/(sin40^(@))=-1/8`
So, the equation having `cos40^(@),cos80^(@)and cos160^(@)` at its roots is
`x^(3)-x^(2)xx0+x xx-3/4-(-(1)/(8))=0or,8x^(3)-6x +1=0`
The equation having `sec 40^(@), sec80^(@) and sec 160^(@)` as its roots is `x^(3)-6x^(2)+8=0`
`thereforesec40^(@)+sec80^(@)+sec160^(@)=6`
115.

If `theta=(2pi)/(2009), then costhetacos 2thetacos3theta... cos1004theta` is

Answer» Correct Answer - C
Let `P=costhetacos2thetacos 3theta...sin1004theta`
Then, `2^(1004)PQ=sin2theta sin4thetasin6theta...sin2008 theta`
`implies2^(1004)PQ=(sin2thetasin4thetasin60...sin2008theta)(sin1006thetasin1008theta...sin2008theta)`
`2^(1004)PQ=(sin2thetasin4thetasin6theta...sin1004theta)`
`{sin(2pi-1003theta)sin(2pi-1001theta)...sin(2pi-theta)}`
`implies2^(1004)PQ=(-1)^(502)sinthetasin2thetasin3thetasin4theta.....sin1003thetasin1001theta`
`implies2^(1004)PQ=QimpliesP=(1)/(2^(1004))`
116.

Statement-1: `cos36^(@)gttan36^(@)` Statement-2: `cos36^(@)gtsin36^(@)`A. Statement-1 is True, Statement-2 is true, Statement-2 is a correct explanation for Statement -1.B. Statement-1 is True, Statement-2 is True, Statement-2 is not a correct explanation for Statement-1.C. Statement-1 is True, Statement-2 is False.D. Statement-1 is False, Statement-2 is True.

Answer» Correct Answer - B
For `0lethetalt(pi)/(4),"we have" cos thetagtsintheta.`
So, statement-2 is true.
Now, `cos36^(@)-tan36^(@)`
`=(cos^(2)36^(@)-sin36^(@))/(cos36^(@))`
`=(1+cos72^(@)-2sin36^(@))/(2cos36^(@))`
`=(1+sin18^(@)-2sin(30^(@)+6))/(2cos36^(@))`
`=(1+2sin9^(@)cos9^(@)-2(sin30^(@)cos6^(@)+cos30^(@)sin60^(@)))/(2cos36^(@))`
`=1+2sin9^(@)cos9^(@)-cos6^(@)-2cos30^(@)sin6^(@)`
`=(1-cos6^(@))+2(sin9^(@)cos9^(@)-cos30^(@)sin6^(@))`
`gt[because1-cos6^(@)gt0and sin9^(@)cos9^(@)gtcos30^(@)sin6^(@)]`
`thereforecos36^(@)-tan36^(@)gt0impliescos36^(@)gttan36^(@)`
So, statement-2 is true. But statement-2 is not a correct explanation for statement-1.
117.

Statement-1: `(cos36^(@)-cos752^(@))/(cos36^(@)cos72^(@))=2` Statement-2: `sin15^(@)=(sqrt6-sqrt7)/(4)`A. Statement-1 is True, Statement-2 is true, Statement-2 is a correct explanation for Statement -1.B. Statement-1 is True, Statement-2 is True, Statement-2 is not a correct explanation for Statement-1.C. Statement-1 is True, Statement-2 is False.D. Statement-1 is False, Statement-2 is True.

Answer» Correct Answer - B
We have,
`(cos36^(@)-cos72^(@))/(cos36^(@)cos72^(@))=(cos36^(@)-sin18^(@))/(cos36^(@)sin18^(@))=((sqrt5+1)/(4)-(sqrt5-1)/(4))/((sqrt5+1)/(4)xx(sqrt5-1)/(4))=2`
So, statement-1 is true.
`sin15^(@)=sin(45^(@)-30^(@))=(sqrt3-1)/(2sqrt2)=(sqrt6-sqrt2)/(4)`
So, statement-2 is also true. But it is not a correct explanation for statement-1.
118.

if `a=cos 2 and b =sin7,` thenA. `a gt0, b gt0`B. `ab lt0`C. `a gtb`D. `a ltb`

Answer» Correct Answer - B
We have, `(pi)/(2)le2^(c)le(3pi)/(4)and 2pilt7^(c)(5pi)/(2)`
`implies2^(c)"is in second quadrant and"7^(c) "is in first quadrnat"`
`impliesa =cos2^(c)lt0and b=sin7^(c)gt0`
`impliesab lt0`
119.

`sqrt(3)cossec2 0^0-sec2 0^0`A. 2B. 1C. 4D. `-4`

Answer» Correct Answer - C
120.

The vlaue of `sqrt3cot20^(@)-4cos20^(@),` isA. 1B. `-1`C. 4D. `-4`

Answer» Correct Answer - A
121.

Biggest among `(sin1+cos1),(sqrt(sin1))+sqrt(cos1)),sqrt(1+sin2)and 1, is`A. `sin1 +cos1`B. `sqrt(sin1)+sqrt(cos1)`C. `sqrt(1+sin2)`D. 1

Answer» Correct Answer - B
We have,
`sqrt(sin1)gtsin1gtsin^(2)1 and, sqrt(cos1)gtcos1 gtcos^(2)1`
`thereforesqrt(sin)1+sqrt(cos1)gtsin1+cos+gt1`
`Also, sqrt(1+sin2)=sqrt(sin^(2)1+cos^(2)1+2 sin1 cos1)=sin1+cos1`
`thereforesqrt(sin1)+sqrt(cos1)gtsqrt(1+sin2)gt1.`
Hence, ` sqrt(sin1)+sqrt(cos1)` is the greatest.
122.

The maximum value of `1+sin(pi/4+theta)+2cos(pi/4-theta)` for real values of `theta` isA. 3B. 5C. 4D. none of these

Answer» Correct Answer - C
We have,
`y=1+sin ((pi)/(4)+theta)+2cos((pi)/(4)-theta)`
`impliesy=1+(1)/(sqrt2)(sin theta+costheta)+sqrt2(cos theta+sin theta)`
`impliesy=1+(sqrt2+(1)/(sqrt2))sintheta+(sqrt2+(1)/(sqrt2))costheta [becausecostheta+sinthetalesqrt2]`
`impliesy=1+(sqrt2+(1)/(sqrt2))(cos theta+sintheta)`
`impliesyle1(sqrt2+(1)/(sqrt2))sqrt2impliesyle4`
Hence, the maximum value is 4,
123.

In a `DeltaABC, if tanA+2tanB=0,` then which one is correct?A. `0lttan^(2)Cle1/8`B. `1/8lttan^(2)Cle1/2`C. `1/2lttan^(2)Clt1`D. none of these

Answer» Correct Answer - A
We have,
`tanA+2tanB=0`
But in a `DeltaABC`
`tanA+tanB+tanC=tanAtanBtanC`
`implies-2tanB+tanB+tanC=-2tan^(2)B tanC [because tanA=-2tanB]`
`implies2 tan ^(2)BtanC-tanB+tanC=0`
Since the B is real. Therefore, `1-8 tan^(2)c ge0`
`impliestan^(2)Cle1/8lttan^(2)Cle1/8`
124.

`tan""(2pi)/(5)-tan""(pi)/(15)-sqrt3tan""(2pi)/(5)tan""(pi)/(15)` is equal toA. `-sqrt3`B. `1//sqrt3`C. 1D. `sqrt3`

Answer» Correct Answer - D
125.

Let `f_k(x) = 1/k(sin^k x + cos^k x)` where `x in RR` and `k gt= 1.` Then `f_4(x) - f_6(x)` equalsA. `1/4`B. `1/12`C. `1/6`D. `1/3`

Answer» Correct Answer - B
We have, `f_(k)(x)=1/k(sin^(k)x+cos^(k)x)`
`thereforef_(4)(x)-f_(6)(x)`
`=1/4(sin^(4)x+cos^(4)x)-1/6(sin^(6)x+cos^(6)x)`
`=1/4{(sin^(2)x+cos^(2)x)^(2)-2sin^(2)xcos^(2)x}`
`-1/6{(sin^(2)x+cos^(2)x)^(3)-3sin^(2)x cos^(2)(sin^(2)x+cos^(2)x)}`
`=1/4(1-2sin^(2)xcos^(2)x)-1/6(1-3sin^(2)xcos^(2)x)=1/12`
126.

If `sec alpha and cosec alpha` are the roots of the equation `x^(2)-ax+b=0,` thenA. `a^(2)=b(b-2)`B. `a^(2)=b(b+2)`C. `a^(2)+b^(2)=2b`D. none of these

Answer» Correct Answer - B
127.

If `tan(x/2)=cosec x - sin x` then the value of `tan^2(x/2)` isA. `2-sqrt5`B. `2+sqrt5`C. `-2-sqrt5`D. none of these

Answer» Correct Answer - D
128.

The value of `cos 10^@ - sin 10^@` isA. positiveB. negativeC. 0D. 1

Answer» Correct Answer - A
129.

If `sinx+cosesx=2,thensin^(n)x+cosec^(n)x` is equal toA. 2B. 2nC. `2n-1`D. `2n-2`

Answer» Correct Answer - A
130.

The value of `cos 1^@ cos 2^@ cos 3^@... cos 179^@` isA. `(1)/(sqrt2)`B. 0C. 1D. none of these

Answer» Correct Answer - B
131.

`1+sinx+sin^(2)x+..."to"oo=2sqrt3 + 4, if` x = ?A. `x=(3pi)/(3)or,(pi)/(3)`B. `x=(7pi)/(6)`C. `x=(pi)/(6)`D. `x=(pi)/(4)`

Answer» Correct Answer - A
132.

Which of the following is correct `sin 1^@ > sin 1`A. `sin1^(@)gtsin1`B. `sin1^(@)ltsin1`C. `sin1^(@)=sin1`D. `sin1^(@)=(pi)/(180)sin1`

Answer» Correct Answer - B
133.

The maximum value of `cos^2(pi/3-x)-cos^2(pi/3+x)`, isA. `(sqrt3)/(2)`B. `1/2`C. `-(sqrt3)/(2)`D. `3/2`

Answer» Correct Answer - A
134.

If `1+sinx+sin^2x+sin^3x+oo`is equal to `4+2sqrt(3),0A. `(pi)/(6)`B. `(pi)/(4)`C. `(pi)/(3)or (pi)/(6)`D. `(pi)/(3)or (2pi)/(3)`

Answer» Correct Answer - D
135.

the value of `tan9^@-tan2 7^@-tan6 3^@+tan8 1^@` is equal toA. 2B. 3C. 4D. 1

Answer» Correct Answer - C
136.

Find the value of log `tan1^0logtan2^0logtan89^0`

Answer» Correct Answer - A
137.

The value of `tan1^@ tan 2^@ tan 3^@ ... tan 89^@` isA. 1B. 0C. `oo`D. `1//2`

Answer» Correct Answer - A
138.

The expression `cosec^(2)A cot^(2)A-sec^(2)A tan^(2)A-(cot^(2)A-tan^(2)A)(sec^(2)A cosec^(2)A-1)` is equal toA. 1B. `-1`C. 0D. 2

Answer» Correct Answer - C
139.

The expression `3{sin^(6)""((pi)/(2)+alpha)+sin^(6)(5pi-alpha)` is equal to

Answer» Correct Answer - B
140.

If `A=130^(@)and x=sinA+cosA,` thenA. `x gt0`B. `xlt0`C. `x=0`D. `x ge0`

Answer» Correct Answer - A
141.

If `tan theta=a/b` then `b cos 2theta+asin 2theta=`A. aB. bC. `b//a`D. `a//b`

Answer» Correct Answer - B
142.

If `abs(cos theta{sin theta+sqrt(sin^2theta+sin^2alpha)})lek`, then the value of kA. `sqrt(1+cos^(2)alpha)`B. `sqrt(1+sin^(2)alpha)`C. `sqrt(2+sin^(2)alpha)`D. `sqrt(2+cos^(2)alpha)`

Answer» Correct Answer - B
143.

The value of `sin10^@+sin20^@+sin30^@...+sin360^@` is equal to -A. 1B. 0C. `-1`D. `1//2`

Answer» Correct Answer - B
144.

`cos.(2pi)/(7)+cos.(4pi)/(7)+cos.(6pi)/(7)`A. 1B. `-1`C. `1//2`D. `-1//2`

Answer» Correct Answer - D
145.

if `sin(alpha+beta)=1 and sin(alpha-beta)=1/2 " "0lealpha,beta,lepi/2,then` find `tan(alpha+2beta)and tan(2alpha+beta)`A. 1B. `-1`C. 0D. `1//2`

Answer» Correct Answer - A
146.

If ABCD is a cyclic quadrilateral, then the value of cosA-cosB+cosC-cosD is equal toA. 1B. 0C. `-1`D. none of these

Answer» Correct Answer - B
147.

If `x+y+z=pi,,tan x tanz=2and tanytanz=18,then tan^(2)z=`A. 15B. 16C. 19D. 20

Answer» Correct Answer - B
Whe have,
`x+y+z=pi`
`impliestanx+tany+tanz=tanxtanyz`
`impliestanx+tany+tanz=2tany" "[becausetanxtanz=2]`
`impliestanx+tanz=tany`
`(tanx+tanz)tanz=tanytanz`
`implies(tanx+tnz)tanz=18`
`impliestanx tanz+tan^(2)z=18`
`implies+tan^(2)z=18impliestan^(2)z=16.`
148.

In a cyclic quadrilateral ABCD, the value of `2+sum cos A soc B,` isA. `sin^(2)A+sin^(2)B,` isB. `sin^(2)B+sin^(2),` DC. `sin^(2)A+sin^(2)C`D. `sin^(2)B+sin^(2)C`

Answer» Correct Answer - A
In the cyclin quadrilateral ABCD, we have `A+C=pi=B+D`
`thereforecos A+cosB+cos C+cosD)^(2)=0`
`implies(cosA+cosB+cosC+cosD)^(2)=0`
`impliescos^(2)A+cosB+cosC+cos^(2)D+2sumcosAcosB=0`
`implies2 cos^(2)A+2cos^(2)B+2sumcosAcosB=0`
`" "[becausecosC=-cosA and cosD=-cosB]`
`impliessum cos A cos B=-[cos^(2)A+cos^(2)B]`
`sumcosAcosB=-2+sin^(2)A+sin^(2)B`
`implies2+sumcos A cos B=sin^(2)A+sin^(2)B=sin^(2)C+sin^(2)D.`
149.

The value of `cot36^(@)cot72^(@),` isA. `1//5`B. `1//sqrt5`C. 1D. `1//3`

Answer» Correct Answer - B
150.

The minimum value of `9tan^2theta+4cot^2theta`is`6``12``4`none of these``A. 13B. 9C. 6D. 12

Answer» Correct Answer - D