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Assertion (A): If A, B, C are the angles...

Assertion (A): If A, B, C are the angles of a triangle such that `cos A + cos B + Cos C = 0 = sin A + sin B + sin C` then `cos 3A + cos 3B + cos 3C = -3`
Reason (R) : If `cos alpha + cos beta + cos gamma = 0 = sin alpha + sin beta + singamma` then `cos 3 alpha + cos 3 beta + cos 3 gamma = 3 cos (gamma+alpha+beta)`

A

Both A and R are true R is correct explanation to A

B

Both A and R are true but R is not correct explanation to A

C

A is true R is false

D

A is false R is true

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The correct Answer is:
A
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AAKASH SERIES-DEMOIVRE'S THEOREM-PRACTICE EXERCISE
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  2. If 1,alpha,alpha^2,…...,alpha^(n-1) are the n^(th) roots of unity, the...

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  3. A : (1+i)^(6)+(1-i)^(6)=0 R : If n is a positive integer then (1+i)^...

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  5. IF omega represents a complex cube root of unity, then (1+1/omega)(1+1...

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  7. If z=(sqrt3-i)/(2) then (i^(101)+z^(101))^(103)=

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  8. The roots of (z-1)^n=i(z+1)^n are plotted on the argand plane they are

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  9. If 'alpha' be the non-real n^(th) roots of unity, then 1+3alpha+5alpha...

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  10. If cos alpha+2cos beta+3cos gamma=sinalpha+2sinbeta+3singamma=0 then s...

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  11. If sin(A+iB)=x+iy then ((x^2)/(sin^2A)-(y^2)/(cos^2A))+((x^2)/(cosh^2B...

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  12. I : sum(k=1)^(6)[sin((2kpi)/(7))-icos((2kpi)/(7))]=i II : sum(r=1)...

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  13. Match the following. {:(Column-I," "Column-II),(I" : "x=costheta...

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  14. The ascending order of the values of z1(1+i)^4+(1-i)^4, z2=(sq...

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  15. I : Value of i^i=e^(-pi/2) II : z=ilog(2+sqrt3) then sinz=2 wh...

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  16. Assertion (A) : (Costheta+iSintheta)^(10)+(Costheta-iSintheta)^(10)=2c...

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  17. The modulus argument form of 1+iTantheta when theta epsilon (pi/2,pi) ...

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  18. If Z=(i^i)^i" where "i=sqrt(-1) then

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  19. If alpha is a non-real and alpha=(1)^(1//5) then the value of 2^(|1+al...

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  20. If (x-1)^4-16=0,then the sum of non-real complex values of x is

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