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If 3 cos x + 2 cos 3x = cos y, 3 sin x +...

If `3 cos x + 2 cos 3x = cos y`, `3 sin x + 2 sin 3x = sin y`, then the value of `cos 2x` is

A

0

B

1

C

`-1`

D

none of these

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The correct Answer is:
A
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MOTION-TRIGNOMETRIC RATIOS & IDENTITIES -Exercise 2(Level -I)
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  3. If alpha in [(pi)/(2),pi] then the value of sqrt(1+ sin alpha)-sqrt(...

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  6. If A=tan6^(@) tan 42^(@) and B= cot 66^(@)cot 78^(@) then-

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  7. The value of 64sqrt(3)sin(pi/48)cos(pi/48)cos(pi/24)cos(pi/12)cos(pi/6...

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  8. Let a and b be positive number not equal to 1 and (3pi)/(2) lt theta ...

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  9. f(theta)=sin^4theta+cos^2theta then range of f(theta)

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  10. The value of cos(pi/19)+cos((3pi)/19)+cos((5pi)/19)+......+cos((17pi)/...

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  11. Value of cos(pi/(2n+1))+cos((3pi)/(2n+1))+cos((5pi)/(2n+1))+... upto ...

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  12. A regular hexagon & a regular dodecagon are inscribed in the same circ...

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  13. in any triangle ABC, which is not right angled Sigma cosA.cosecB.cosec...

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  14. If 3 cos x + 2 cos 3x = cos y, 3 sin x + 2 sin 3x = sin y, then the va...

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  15. of 0 < x < 90^@ and cosx=3/sqrt10 then the value of log10 sinx+log10 c...

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  16. if tantheta=1/(2+(1/(2+1/(2+...oo)))) then find possible values of the...

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  18. If 2 cos x +sin x=1 then value of 7 cos x + 6 sin x lis equal to

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  19. Let f(x) denote the sum of the infinite trigonometric series f(x)=unde...

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  20. If tan A & tan B are the roots of the quadratic equation x^2 - ax +...

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