Home
Class 12
MATHS
Consider the equation 5 sin^2 x + 3 sin ...

Consider the equation `5 sin^2 x + 3 sin x cos x - 3 cos^2 x =2 `.......... (i)
`sin^2 x - cos 2 x =2-sin 2 x `........... (ii)
If ` tan alpha , tan beta ` satisfy (i) and ` cos gamma , cos delta ` satisfy (ii) , then ` tan alpha * tan beta + cos gamma + cos delta ` can be equal to

A

a) `-1`

B

b) `-(5)/(3)+(2)/(sqrt(13))`

C

c) `(5)/(3)-(2)/(sqrt(13)) `

D

d) `(5)/(3)+(2)/(sqrt(13))`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the given problem step-by-step, we will analyze the two equations provided and derive the required expression. ### Step 1: Solve the first equation The first equation is: \[ 5 \sin^2 x + 3 \sin x \cos x - 3 \cos^2 x = 2 \] We can rearrange this equation: \[ 5 \sin^2 x + 3 \sin x \cos x - 3 \cos^2 x - 2 = 0 \] Next, we divide the entire equation by \( \cos^2 x \): \[ 5 \tan^2 x + 3 \tan x - 3 - 2 \sec^2 x = 0 \] Using the identity \( \sec^2 x = 1 + \tan^2 x \), we can substitute: \[ 5 \tan^2 x + 3 \tan x - 3 - 2(1 + \tan^2 x) = 0 \] This simplifies to: \[ 5 \tan^2 x + 3 \tan x - 3 - 2 - 2 \tan^2 x = 0 \] \[ (5 - 2) \tan^2 x + 3 \tan x - 5 = 0 \] \[ 3 \tan^2 x + 3 \tan x - 5 = 0 \] Let \( t = \tan x \): \[ 3t^2 + 3t - 5 = 0 \] ### Step 2: Solve the quadratic equation Using the quadratic formula \( t = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \): Here, \( a = 3, b = 3, c = -5 \): \[ t = \frac{-3 \pm \sqrt{3^2 - 4 \cdot 3 \cdot (-5)}}{2 \cdot 3} \] \[ t = \frac{-3 \pm \sqrt{9 + 60}}{6} \] \[ t = \frac{-3 \pm \sqrt{69}}{6} \] Thus, we have: \[ \tan \alpha = \frac{-3 + \sqrt{69}}{6}, \quad \tan \beta = \frac{-3 - \sqrt{69}}{6} \] ### Step 3: Solve the second equation The second equation is: \[ \sin^2 x - \cos 2x = 2 - \sin 2x \] Using the identities \( \cos 2x = \cos^2 x - \sin^2 x \) and \( \sin 2x = 2 \sin x \cos x \): \[ \sin^2 x - (\cos^2 x - \sin^2 x) = 2 - 2 \sin x \cos x \] This simplifies to: \[ 2 \sin^2 x + \cos^2 x = 2 - 2 \sin x \cos x \] Using \( \cos^2 x = 1 - \sin^2 x \): \[ 2 \sin^2 x + (1 - \sin^2 x) = 2 - 2 \sin x \cos x \] \[ 2 \sin^2 x + 1 - \sin^2 x = 2 - 2 \sin x \cos x \] \[ \sin^2 x + 2 \sin x \cos x - 1 = 0 \] ### Step 4: Solve for \( \cos x \) Using the identity \( \sin^2 x = 1 - \cos^2 x \): \[ 1 - \cos^2 x + 2 \sin x \cos x - 1 = 0 \] \[ -\cos^2 x + 2 \sin x \cos x = 0 \] Factoring out \( \cos x \): \[ \cos x (2 \sin x - \cos x) = 0 \] Thus, \( \cos x = 0 \) or \( 2 \sin x - \cos x = 0 \). ### Step 5: Find values of \( \cos \gamma \) and \( \cos \delta \) If \( \cos x = 0 \), then \( \cos \gamma = 0 \) or \( \cos \delta = 0 \). If \( 2 \sin x - \cos x = 0 \), then \( \sin x = \frac{1}{2} \cos x \). ### Step 6: Calculate the final expression We need to find: \[ \tan \alpha \tan \beta + \cos \gamma + \cos \delta \] Calculating \( \tan \alpha \tan \beta \): \[ \tan \alpha \tan \beta = \left(\frac{-3 + \sqrt{69}}{6}\right)\left(\frac{-3 - \sqrt{69}}{6}\right) = \frac{(-3)^2 - (\sqrt{69})^2}{36} = \frac{9 - 69}{36} = \frac{-60}{36} = -\frac{5}{3} \] Assuming \( \cos \gamma = 0 \) and \( \cos \delta = 0 \): \[ \tan \alpha \tan \beta + \cos \gamma + \cos \delta = -\frac{5}{3} + 0 + 0 = -\frac{5}{3} \] ### Final Answer Thus, the final value is: \[ \boxed{-\frac{5}{3}} \]
Promotional Banner

Topper's Solved these Questions

  • TRIGONOMETRIC EQUATIONS AND INEQUATIONS

    ARIHANT MATHS ENGLISH|Exercise Exercise (Single Integer Answer Type Questions)|11 Videos
  • TRIGONOMETRIC EQUATIONS AND INEQUATIONS

    ARIHANT MATHS ENGLISH|Exercise Exercise (Statement I And Ii Type Questions)|6 Videos
  • TRIGONOMETRIC EQUATIONS AND INEQUATIONS

    ARIHANT MATHS ENGLISH|Exercise Exercise (More Than One Correct Option Type Questions)|25 Videos
  • THREE DIMENSIONAL COORDINATE SYSTEM

    ARIHANT MATHS ENGLISH|Exercise Three Dimensional Coordinate System Exercise 12 : Question Asked in Previous Years Exam|2 Videos
  • TRIGONOMETRIC FUNCTIONS AND IDENTITIES

    ARIHANT MATHS ENGLISH|Exercise Exercise (Questions Asked In Previous 13 Years Exam)|19 Videos

Similar Questions

Explore conceptually related problems

Consider the equation 5 sin^2 x + 3 sin x cos x - 3 cos^2 x =2 .......... (i) sin^2 x - cos 2 x =2-sin 2 x ........... (ii) If alpha is a root (i) and beta is a root of (ii), then tan alpha + tan beta can be equal to

Consider the equation 5 sin^2 x + 3 sin x cos x - 3 cos^2 x =2 .......... (i) sin^2 x - cos 2 x =2-sin 2 x ........... (ii) The number of solutions common to (i) and (ii) is 0 1 finite infinite

Prove that : (sin x + sin 3x)/(cos x + cos 3x) = tan 2x

Solve the equation ( cos x - sin x )(2 tan x +(1)/( cos x ))+2 =0

(sin 7x + sin 3x )/(cos 7x + cos 3x ) = tan 5x.

Prove that (sin 5x - 2 sin 3 x + sin x )/( cos 5 x - cos x ) = tan x

If tan beta=2sin alpha sin gamma co sec(alpha+gamma) , then cot alpha,cot beta,cotgamma are in

If 2 sin alphacos beta sin gamma=sinbeta sin(alpha+gamma),then tan alpha,tan beta and gamma are in

If cos alpha + cos beta + cos gamma = 0 and also sin alpha + sin beta + sin gamma= 0, then prove that: cos 3 alpha + cos 3beta + cos 3gamma = 3 cos (alpha + beta + gamma)

Prove that : (sin x - sin y)/(cos x + cos y) = tan ((x-y)/2)