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Solve 5 cos 2 theta+2 "cos"^(2) theta/2 ...

Solve `5 cos 2 theta+2 "cos"^(2) theta/2 +1=0, -pi lt theta lt pi`.

A

`(pi)/(3)`

B

`(pi)/(3), "cos"^(-1) (3//5)`

C

`"cos"^(-1)(3//5)`

D

`(pi)/(3), pi-"cos"^(-1)(3//5)`

Text Solution

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The correct Answer is:
D
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OBJECTIVE RD SHARMA ENGLISH-TRIGONOMETRIC EQUATIONS AND INEQUATIONS-Exercise
  1. The equation "sin" theta = x +(p)/(x) for real values of x is possible...

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  2. If sin A = sin B and cos A= cos B, then find the value of a in terms o...

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  3. Solve 5 cos 2 theta+2 "cos"^(2) theta/2 +1=0, -pi lt theta lt pi.

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  4. If (1+tantheta)(1+tanphi)=2, then theta + phi=

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  5. The general solution of "tan" 3x =1, is

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  6. If 1+sintheta+sin^2theta+sin^3theta+..to oo=4+2sqrt3 0<theta<pi, t...

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  7. If alpha a n d beta are the solutions of the equation at a ntheta+bs e...

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  8. Solve sinx+siny=sin(x+y)a n d|x|+|y|=1

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  9. The expression (1 + tan x + tan^2 x)(1-cot x + cot^2 x) has the positi...

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  10. If the the equation a sin x + cos 2x=2a-7 possesses a solution, then f...

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  11. The equation "sin"^(6) x + "cos"^(6) x = lambda, has a solution if

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  12. If y + "cos" theta = "sin" theta has a real solution, then

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  13. The solution set of the equation 4 sin theta. Cos theta-2 cos theta-2s...

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  14. The most general solution of tan theta =-1 and cos theta = 1/(sqrt(2))...

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  15. The complex numbers sin x +i cos 2x and cos x -i sin 2x are conjugate ...

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  16. The smallest positive root of the equation tanx-x=0 lies in (0,pi/2) ...

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  17. The number of solutions of the equation "sin" x = "cos" 3x " in " [0, ...

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  18. Find the general values of theta satisfying tan theta + tan ((3pi)/...

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  19. If sin theta+ cos theta = sqrt(2) cos theta, (theta ne 90^(@)) then v...

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  20. The number of solutions of the equation tanx+secx=2cosx lying in the i...

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