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If cosA+cosB+cosC=0,sinA+sinB+sinC=0andA...

If `cosA+cosB+cosC=0,sinA+sinB+sinC=0andA+B+C=180^(@)` then the value of `cos3A+cos3B+cos3C` is :

A

3

B

`-3`

C

`sqrt(3)`

D

0

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The correct Answer is:
b
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OBJECTIVE RD SHARMA ENGLISH-COMPLEX NUMBERS -Chapter Test
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  3. If cosA+cosB+cosC=0,sinA+sinB+sinC=0andA+B+C=180^(@) then the value of...

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  4. Find the sum 1xx(2-omega)xx(2-omega^(2))+2xx(-3-omega)xx(3-omega^(2))+...

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  5. The value of the expression (1+(1)/(omega))+(1+(1)/(omega^(2)))+(2+(1)...

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  6. The condition that x^(n+1)-x^(n)+1 shall be divisible by x^(2)-x+1 is ...

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  7. The expression (1+i)^(n1)+(1+i^(3))^(n2) is real iff

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  8. If |{:(6i,3i,1),(4,3i,-1),(20,3,i):}|=x+iy, then (x, y) is equal to

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  9. If cosalpha+2cosbeta+3cosgamma=sinalpha+2sinbeta+3singamma=0,t h e nt ...

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  10. If cosalpha+2cosbeta+3cosgamma=sinalpha+2sinbeta+3singamma=0,t h e nt ...

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  11. Sum of the series sum(r=0)^n (-1)^r ^nCr[i^(5r)+i^(6r)+i^(7r)+i^(8r)] ...

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  12. If az(1)+bz(2)+cz(3)=0 for complex numbers z(1),z(2),z(3) and real num...

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  13. If 2z1-3z2 + z3=0, then z1, z2 and z3 are represented by

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  14. If Re((z+4)/(2z-1)) = 1/2 then z is represented by a point lying on

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  15. The vertices of a square are z(1),z(2),z(3) and z(4) taken in the anti...

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  16. Let lambda in R . If the origin and the non-real roots of 2z^2+2z+lam...

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  17. If z(1),z(2),z(3), represent vertices of an equilateral triangle such ...

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  18. If P,P^(') represent the complex number z(1) and its additive inverse ...

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  19. Let A(z(1)),B(z(2)),C(z(3)) be the vertices of an equilateral triangle...

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  20. The area of the triangle (in square units) whose vertices are i, omega...

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