Home
Class 12
MATHS
Let A and B denote the statements A : ...

Let `A and B` denote the statements
`A : cos alpha + cos beta + cos gamma =0`
`B : sin alpha + siin beta + sin gamma = 0`
If `cos(beta - gamma) + cos (gamma -alpha) + cos (alpha -beta) = - (3)/(2)`,
then

A

`A` is true and `B` is false.

B

`A` is false and `B` is true.

C

Both `A and B` are true.

D

Both `A and B` are false.

Text Solution

Verified by Experts

The correct Answer is:
C

` cos (beta -gamma) +cos (gamma - alpha ) + cos (alphea - beta) =-(3)/(2)`
`rArr 2 [cos (beta -gamma) +cos (gamma -alpha ) + cos (alpha - beta)] + 3 =0`
`rArr 2 [cos (beta -gamma ) + cos (gamma -alpha) + cos (alpha -beta)] + sin ^(2) alpha + cos ^(2) alpha + sin ^(2) beta + cos ^(2) beta + sin ^(2) gamma + cos ^(2) gamma =0`
`rArr (sin alpha + sin beta + sin gamma)^(2) + ( cos alpha + cos beta + cos gamma)^(2) =0`
`rArr cos alpha + cos beta + cos gamma =0`
and `sin alpha + sin beta + sin gamma =0`
Doubtnut Promotions Banner Mobile Dark
|

Topper's Solved these Questions

  • TRIGONOMETRIC RATIOS AND TRANSFORMATION FORMULAS

    CENGAGE|Exercise JEE Advanced Previous Year|5 Videos
  • TRIGONOMETRIC RATIOS AND TRANSFORMATION FORMULAS

    CENGAGE|Exercise Matrix Match Type|1 Videos
  • TRIGONOMETRIC RATIOS AND TRANSFORMATION FORMULAS

    CENGAGE|Exercise Exercise (Numerical)|38 Videos
  • TRIGONOMETRIC FUNCTIONS

    CENGAGE|Exercise SINGLE CORRECT ANSWER TYPE|38 Videos
  • TRIGONOMETRIC RATIOS FOR COMPOUND, MULTIPLE, SUB-MULTIPLE ANGLES, AND TRANSFORMATION FORMULAS

    CENGAGE|Exercise Multiple Correct Answers Type|6 Videos

Similar Questions

Explore conceptually related problems

If cos alpha + cos beta + cos gamma = sin alpha + sin beta + sin gamma = 0 , show that cos 3alpha + cos 3 beta + cos gamma = 3 cos (alpha + beta + gamma) and

If cos alpha + cos beta + cos gamma = sin alpha + sin beta + sin gamma = 0 , show that sin 3alpha + sin 3 beta + sin 3gamma = 3 sin (alpha + beta + gamma)

Knowledge Check

  • If alpha , beta , gamma in [0,pi] and if alpha , beta , gamma are in A.P then ( sin alpha - sin gamma)/( cos gamma -cos alpha) is equal to

    A
    `sin beta `
    B
    `cos beta `
    C
    `cot beta `
    D
    `2 cos beta `
  • Similar Questions

    Explore conceptually related problems

    If cos alpha + cos beta = 1//2 and sin alpha+ sin beta = 1//3 , then

    Prove that : cos^2 (beta-gamma) + cos^2 (gamma-alpha) + cos^2 (alpha-beta) =1+2cos (beta-gamma) cos (gamma-alpha) cos (alpha-beta) .

    If cos alpha + cos beta =0 = sin alpha + sin beta , then cos 2 alpha + cos 2 beta is equal to

    Evaluate {:[( cos alpha cos beta , cos alpha sin beta , -sin alpha ),( -sin beta , cos beta, 0),( sin alpha cos beta, sin alpha sin beta, cos alpha ) ]:} =0

    IF cos ( alpha + beta ) =0 then sin ( alpha + 2 beta ) is equal to

    If cos (alpha - beta) + cos (beta - gamma) + cos (gamma - alpha) = (-3)/(2) then prove that cos alpha + cos beta+ cos gamma = sin alpha + sin beta + sin gamma = 0 .

    Prove that 2 sin^2 beta + 4 cos(alpha + beta) sin alpha sin beta + cos 2(alpha + beta) = cos 2alpha