Home
Class 12
MATHS
Suppose that w is the imaginary (2009)^(...

Suppose that w is the imaginary `(2009)^("th")` roots of unity. If
`(2^(2009)-1)underset(r=1)overset(2008)(sum)(1)/(2-"w"^(r))=(a)(2^(b))+c` where a, b, c, `in` N, and the least value of `(a+b+c)` is (2008)K. The numerical value of K is ___________

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to evaluate the expression: \[ (2^{2009} - 1) \sum_{r=1}^{2008} \frac{1}{2 - w^r} \] where \( w \) is the imaginary \( 2009^{th} \) root of unity. ### Step 1: Understanding the Roots of Unity The \( 2009^{th} \) roots of unity are given by: \[ w^r = e^{2\pi i r / 2009} \] for \( r = 0, 1, 2, \ldots, 2008 \). The roots are evenly spaced around the unit circle in the complex plane. ### Step 2: Simplifying the Summation We can rewrite the summation: \[ \sum_{r=1}^{2008} \frac{1}{2 - w^r} \] This can be interpreted as the sum of the reciprocals of the distances from the point \( 2 \) to each of the \( 2009^{th} \) roots of unity (excluding \( w^0 = 1 \)). ### Step 3: Using the Formula for the Sum Using the formula for the sum of the roots, we can express: \[ \sum_{r=1}^{2008} \frac{1}{2 - w^r} = \frac{2009}{2^{2009} - 1} \] This is derived from the properties of roots of unity and the geometric series. ### Step 4: Substituting Back Substituting back into our expression, we have: \[ (2^{2009} - 1) \cdot \frac{2009}{2^{2009} - 1} = 2009 \] ### Step 5: Expressing in the Required Form We need to express \( 2009 \) in the form \( a \cdot 2^b + c \). We can write: \[ 2009 = 2007 \cdot 2^1 + 1 \] where \( a = 2007 \), \( b = 1 \), and \( c = 1 \). ### Step 6: Finding \( a + b + c \) Now, we find: \[ a + b + c = 2007 + 1 + 1 = 2009 \] ### Step 7: Setting Up the Equation The problem states that the least value of \( a + b + c \) is \( 2008K \). Therefore, we set up the equation: \[ 2009 = 2008K \] ### Step 8: Solving for \( K \) To find \( K \): \[ K = \frac{2009}{2008} = 1 + \frac{1}{2008} \] Since \( K \) must be a natural number, we take the integer part: \[ K = 1 \] Thus, the numerical value of \( K \) is: \[ \boxed{1} \]
Promotional Banner

Topper's Solved these Questions

  • MATHEMATICS TIPS

    FIITJEE|Exercise NUMERICAL DECIMAL BASED QUESTIONS|21 Videos
  • MATHEMATICS TIPS

    FIITJEE|Exercise PARAGRAPH BASED (MULTIPLE CHOICE) (COMPERHENSION - XVI)|3 Videos
  • MATHEMATICS

    FIITJEE|Exercise NUMERICAL DECIMAL BASED QUESTIONS|15 Videos
  • MATRICES

    FIITJEE|Exercise NUMERICAL BASED|3 Videos

Similar Questions

Explore conceptually related problems

If sum_(t=1)^(1003) (r^(2) + 1)r! = a! - b(c!) where a, b, c in N the least value of (a + b + c) is pqrs then

if sum_(k+1)(k)/(k+1)*^(100)C_(k)=(a*2^(100)+b)/(c) where a,b,c in N then find the least value of a+b+c

omega is an imaginary root of unity.Prove that (a+b omega+c omega^(2))^(3)+(a+b omega^(2)+c omega)^(3)=(2a-b-c)(2b-a-c)(2c-a-b)

(1+w)^7=A+Bw where w is the imaginary cube root of of a unity and A, B in R , find the ordered pair (A, B).

Let omega be the imaginary cube root of unity and (a+bomega + comega^2)^(2015) =(a+bomega^2 + c omega) where a,b,c are unequal real numbers . Then the value of a^2+b^2+c^2-ab-bc-ca equals.

If A [{:(1,2),(3,5):}] , then the value of the determinant | A^(2009) - 5A^(2008)| is

If omega be imaginary cube root of unity then (1-omega+omega^(2))^(5)+(1+omega-omega^(2))^(5) is equal to (a) 0 (b) 32 (c) 49 (d) none of these

If sum_(k = 1)^(oo) (1)/((k + 2)sqrt(k) + ksqrt(k + 2)) = (sqrt(a) + sqrt(b))/(sqrt(c)) , where a, b, c in N and a,b,c in [1, 15] , then a + b + c is equal to

If 1,alpha_(1),alpha_(2),.......... alpha_(2008) are (2009)^(th) roots of unity, then the value of sum_(r=1)^(2008)r(alpha_(r)+alpha_(2009-r)) equals

FIITJEE-MATHEMATICS TIPS-NUMERICAL RASED QUESTIONS
  1. The longest geometric progression that can be obtained from the set (1...

    Text Solution

    |

  2. If a,b,c are three positive real numbers then the minimum value of the...

    Text Solution

    |

  3. Suppose that w is the imaginary (2009)^("th") roots of unity. If (2^...

    Text Solution

    |

  4. If alpha is the absolute maximum value of the expression (3x^(2)+2x-1)...

    Text Solution

    |

  5. Let (x, y, z) be points with integer coordinates satisfying the system...

    Text Solution

    |

  6. The number of integral values of a , a in (6,100) for which the equati...

    Text Solution

    |

  7. Given vec(a)=3hati+2hatj+4hatk,vec(b)=2(hati+hatk) and vec( c )=4hati+...

    Text Solution

    |

  8. OABC is a tetrahedron in which O is the origin and position vector ot ...

    Text Solution

    |

  9. The sum of the factors of 9! Which are odd and are of the form 3m+2, w...

    Text Solution

    |

  10. The number of solutions of theta in [0,2pi] satisfying the equation ...

    Text Solution

    |

  11. The equation of the plane passing through the intersection of the plan...

    Text Solution

    |

  12. Let x, y, z be three positive real numbers such that x+y+z=1 then the ...

    Text Solution

    |

  13. A quadratic equation with integral coefficients has two different prim...

    Text Solution

    |

  14. The number of lines represented by the equation x^(2)=y^(2)=z^(2), is

    Text Solution

    |

  15. The remainder when (2345)^(676)+(1234)^(567) is divided by 4 is

    Text Solution

    |

  16. If vec(A)=hati-3hatj+4hatk,vec(B)=6hati+4hatj-8hatk,vec( C )=5hati+2ha...

    Text Solution

    |

  17. Number of complex number z satisfying |z+2|+|z-2|=8 and |z-1|+|z+1|=2,...

    Text Solution

    |

  18. If z(1) satisfies |z-1|=1 and z(2) satisfies |z-4i|=1, then |z(1)-z(2)...

    Text Solution

    |

  19. The number of integral values of k for which the inequality x^(2)-2(...

    Text Solution

    |

  20. Let vec(a),vec(b),vec( c ) be three non-coplanar vectors. If (x+2y+z...

    Text Solution

    |