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All questions of Trigonometric Functions and Equations for Grade 12 Exam

Can you explain the answer of this question below:

  • A:

    4

  • B:

    1/4

  • C:

    2

  • D:

    none of these.

The answer is a.

Shivani answered
->>Sintheta=3/5....-> sectheta=1/costheta...-> tantheta=sintheta/costheta...by substituting in the given que u will get...1+sintheta/1-sintheta....at last by solving u will get ans 4...HOPE U GOT IT...

Evaluate sin(3 sin–10.4)
​a)0.56
b)0.31
c)0.64
d)0.9
Correct answer is 'D'. Can you explain this answer?

3sin^-1(x) = sin^-1(3x - 4x^3) when -1/2<=x<=1/2
Definitely 0.4 comes in this range of x and so
3sin^-1(0.4) = sin^-1[3*0.4 - 4*0.4^3]
3sin^-1(0.4) = sin^-1[1.2 - 4*0.064]
3sin^-1(0.4) = sin^-1[1.2 - 0.256]
3sin^-1(0.4) = sin^-1[0.944]
Finally , sin(3sin^-1(0.4)) = sin{sin^-1(0.944)} = 0.944

The maximum value of sin x + cos x is
  • a)
    1
  • b)
    2
  • c)
    √2
  • d)
Correct answer is option 'C'. Can you explain this answer?

Shreya Gupta answered
sinx + cosx=sinx + sin(90-x)=2sin{(x+90-x)/2}cos{(x-90+x)/2}using the formula 

The simplest form of for x > 0 is …​
  • a)
    x
  • b)
    -x/2
  • c)
    2x
  • d)
    x/2
Correct answer is option 'D'. Can you explain this answer?

Mira Joshi answered
tan-1(1-cosx/1+cosx)½
= tan-1{(2sin2 x/2) / (2cos2 x/2)}½
= tan-1{(2sin2 x/2) / (2cos2 x/2)}
= tan-1(tan x/2)
= x/2

Evaluate :cos (tan–1 x)
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'B'. Can you explain this answer?

Sushil Kumar answered
tan−1 x = θ , so that  x=tanθ . We need to determine  cosθ .
sec2θ = 1 + tan2θ = 1 + x2 
∴s ecθ = ±√(1+x2
Then, cos(tan−1x) = cosθ=1/secθ = ±1/√(1+x2)

sin2000+cos2000 is
  • a)
    Negative
  • b)
    Positive
  • c)
    Zero
  • d)
    Zero or positive.
Correct answer is option 'A'. Can you explain this answer?

Mihir Joshi answered
Because both sin 200and cos 2000 lies in 3rd quadrant. In 3rd quadrant values of both sine and cosine functions are negative.

  • a)
    4
  • b)
    1/4
  • c)
    2
  • d)
    none of these.
Correct answer is option 'A'. Can you explain this answer?

Krishna Iyer answered
sin θ is 3/5.
on simplifying:
(secθ + tanθ)/(secθ - tanθ)
We get, (1+sin θ)/(1-sin θ)
=(1+3/5)/(1-3/5)
=(8/2)
=4

The value ofcos150−sin150 is
  • a)
  • b)
  • c)
    0
  • d)
     
Correct answer is option 'D'. Can you explain this answer?

Poojan Angiras answered
Heyy!!! write cos 15 and sin 15 as cos(60-45) and sin(60-45) respectively.And then apply formula of cos(a+b) and sin(a+b).Proceed as the question u will get correct answer :-):-)^_^

If ab + bc + ca = 0, then find 1/a2-bc + 1/b2 – ca + 1/c2- ab
  • a)
    π
  • b)
    0
  • c)
    -1
  • d)
Correct answer is option 'B'. Can you explain this answer?

Preeti Iyer answered
Given ab+bc+ca=0 and asked to find value 1/(a2-bc ) + 1/(c2-ab) + 1/(a2-bc)Put -ac = ab + bc ; -ab = ac+ bc and -bc =ab + 

The number of solutions of the equation sin-1 x - cos-1 x = sin-1(1/2) is
a) 3
b) 1
c) 2
d) infinite.
Correct answer is option 'B'. Can you explain this answer?

Solution:

Given equation is sin^-1(x) - cos^-1(x) = sin^-1(1/2)

We know that sin(x) + cos(x) = √2 cos(x - π/4)

So, sin^-1(x) - cos^-1(x) = π/2 - sin^-1(√2x)

Therefore, the given equation becomes π/2 - sin^-1(√2x) = sin^-1(1/2)

sin(sin^-1(x)) = xsin(π/2 - sin^-1(√2x)) = √[1 - 2x^2]

√[1 - 2x^2] = 1/2

2x^2 = 3/4

x = ±√3/2

Therefore, the given equation has only 1 solution, which is x = √3/2 or x = -√3/2.

Hence, the correct answer is option B.

Evaluate: sin (2 sin–10.6)​
  • a)
    0.6
  • b)
    0.66
  • c)
    0.36
  • d)
    0.96
Correct answer is option 'D'. Can you explain this answer?

Nikita Singh answered
Let, sin-1(0.6) = A…………(1)
  ( Since, sin² A + cos² A = 1 ⇒ sin² A = 1 - cos² A ⇒ sin A = √(1-cos² A) )

  • a)
    ±√3.
  • b)
    0
  • c)
  • d)
    1
Correct answer is option 'D'. Can you explain this answer?

Devendra Singh answered
Apply apply formula of Sin inverse X + Cos inverse X and the question will be solved

  • a)
  • b)
    1
  • c)
    0
  • d)
    none of these.
Correct answer is option 'B'. Can you explain this answer?

Nikita Singh answered
sin-1√3/5 = A
Sin A = √3/5 , cos A = √22/5 
Therefore Cos-1√3/5 = B
Cos B = √3/5 , sin B = √22/5  
sin(A+B) = sinA cosB + cosA sinB
= √3/5 * √3/5 + √22/5 * √22/5
= 3/25 * 22/25
= 25/25 
= 1

Evaluate 
  • a)
  • b)
  • c)
  • d)
Correct answer is 'A'. Can you explain this answer?

Ritu Singh answered
Correct Answer :- a
Explanation : cos-1(12/13) + sin-1 (3/5)
⇒ sin-1 5/13 + sin-1 3/5 
Using the formula,  sin-1x +  sin-1y = sin-1( x√1-y² + y√1-x² )
⇒ sin-1 ( 5/13√1-9/25 + 3√1-25/169)
⇒ sin-1 ( 5/13 × 4/5 + 3/5 × 12/13)
⇒ sin-1 (30 + 36 / 65)
⇒ sin-1 (56/ 65)

  • a)
    4
  • b)
    1/4
  • c)
    2
  • d)
    none of these.
Correct answer is 'A'. Can you explain this answer?

SinQ is 3/5.
on simplifying:
(secQ+tanQ)/(secQ-tanQ)
We get...(1+sinQ)/(1-sinQ)
=(1+3/5)/(1-3/5)
=(8/2)
=4

The simplest form of 
  • a)
  • b)
  • c)
    2x
  • d)
Correct answer is option 'A'. Can you explain this answer?

Seelam Yogitha answered
Divide inner functions(both nr n Dr) with cosx,, tan^-(1-tanx/1+tanx)=tan^-(tan(π/4 -X) )=π/4 -x

Evaluate sin(3 sin–1 0.4)​
  • a)
    0.9
  • b)
    0.31
  • c)
    0.64
  • d)
    0.56
Correct answer is option 'D'. Can you explain this answer?

Mira Sharma answered
sin(3 sin^−1 0.4)
= sin[sin^−1(3 x 0.4−4 x 0.4^2)]      [∵3sin^−1 x = sin^−1(3x − 4x^3)]
= sin[sin^−1(1.2 − 4 x 0.16)]
= sin[sin^−1(1.2 − 0.64)]
= sin[sin^−1(0.56)] = 0.56

 is equal to
  • a)
  • b)
  • c)
  • d)
Correct answer is 'C'. Can you explain this answer?

Nikita Singh answered
Let y = tan−1[(a−x)/(a+x)]1/2
put x = a cos θ
Now, y = tan−1[(a − a cos θ)/(a + a cos θ)]1/2
⇒ y = tan−1((1 − cos θ)/(1 + cos θ))1/2
⇒ y = tan−1[[(1−cos θ)(1−cos θ)]/(1+cos θ)(1−cos θ)]1/2
⇒ y = tan−1[(1−cos θ)2/1 − cos2θ]1/2
⇒ y = tan−1[(1 − cos θ)/sin θ]
⇒ y = tan−1[2 sin2(θ/2)/2 sin(θ/2) . cos(θ/2)]
⇒ y = tan−1[tan(θ/2)]
⇒ y = θ/2
⇒ y = 1/2 cos−1(x/a)

Value of 
  • a)
  • b)
    tan-1 3 + tan-1 2x.
  • c)
  • d)
    tan-1 6 + tan-1 x.
Correct answer is option 'A'. Can you explain this answer?

Tejas Verma answered
tan-1[(3+2x)/(2-3x)]
=> tan-1[2(3/2 + x)/2(1-3/2x)]
=> tan-1[(3/2 + x)/(1-3/2x)]
=> tan-1(3/2) + tan-1(x)

sin (200)0 + cos (200)0 is
  • a)
    Zero
  • b)
    Positive
  • c)
    Zero or positive.
  • d)
    Negative
Correct answer is option 'D'. Can you explain this answer?

Because both sin 2000 and cos 2000 lies in 3rd quadrant. In 3rd quadrant values of sin and cos are negative.

If 2tan−1(cos x) = tan−1(2cosecx) , then x =
  • a)
  • b)
  • c)
  • d)
    none of these.
Correct answer is option 'B'. Can you explain this answer?

If 2 tan-1 (cos x) = tan -1(2 cosec x),
2tan-1(cos x) = tan-1 (2 cosec x)
= tan-1(2 cosec x) 
= cot x cosec x = cosec x = x = π/4

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