Saturday, 11 December 2021

QUICK REVISION (COMPLEX NUMBER)

A) SHORT ANSWER TYPE & OBJECTIVE QUESTIONS:

1) Find the conjugate of the complex number (2+3i)/(2-3i).    5/13 - 12i/13

2) find the modulus of (1-i)³/(1-i³). 2

3) Find the amplitude of -3- 3i.   -3π/4

4) Resolve into factors: a²+ ab+ b².       (a- bw)(a- bw²)

5) Find the square root of -i.       ±1/√2(1- i)

6) Evaluate : (1- w²)(1- w⁴)(1- w⁸)(1- w¹⁶).                       9

7) If z= x+ iy and |z- 2| = |2z - 1|, Prove that, x² + y² = 1.

8) Find the smallest positive integers n for which {(1+i)/(1 - i)}ⁿ = 1.               4

9) Find the square root of q+ √(q² -1), 0< q <1.            ±1/√2 {√(1+q)+ i √(2-q)}

10) If x= a+ b, y= aw + bw², z= aw² + be, find xyz.                            a³ + b³

11) Solve: |z| - z = 1+ 2i, (z= x+ i y).            3/2 - 2i

12) The sum and the product of two complex numbers are respectively 6 and 25. Find the numbers.      3±4i

13) Determine the three cube roots of i.                       i, (i+√3)/2

14) If z= x + i y and (z -1)/(z+1) is purely imaginary, prove that, |z| = 1.

15) The absolute value of (i/2) is.
A) i/2.  B) 1/2.    C) 1/√2    D) none

16) The value of √4 . √9 is
A) 6     B) -6.    C) -6 or 6    D) none

17) The value of w⁴+ w⁸+ 1/w .1/w² is
A) w   B) w².  C) -1      D) 0.

18) The argument of ia(a< 0), is.
A) 0      B) π/2      C) 3π/2.      D) π

19) The value of (1- w +w²)⁵ + (1+ w -w²)⁵ is..
A) -1      B) 1      C) -32        D) 32.

20) The amplitude of (a+ i b)² is
A) tan⁻¹(b/a)      B) 2tan⁻¹(b/a).
C) 2tan⁻¹(a/b)   D) tan⁻¹(a/b)

21) If z= x + i y, the value of (amp z + amp z') is.
A) 0   B) π/2  C) π       D) none.

22) the quantity, whose cube root is 1/2 (√3 + i), is.
A) -1      B) 1     C) -i       D) i.

23) The value of (1+ w)(1+ w²)(1+ w⁴)(1- w⁸)....2n factors, is
A) 1.       B) 2ⁿ       C) -1       D) wⁿ

24) For any complex number z, the minimum value of |z | + |z - 1| is...
A) 0      B) 1/2      C) 1.       D) 3/2

25) The real part of (2- i)²/(2+ i) is
A) -2/5   B) -6/5    C) -11/5   D) none



B) GENERAL QUESTIONS:

1) Show that (1- w+ w²) (1- w²+w⁴) (1- w⁴+ w⁸)....2n factors = 2²ⁿ.

2) If X+ i Y be one of the cube root of x + i y, prove that, 4(X² - Y²)= x/X + y/Y.

3) If x= a + i b, y= a¢+ b$, z= a$ + b¢, where ¢, $ are complex cube roots of unity, show that x³ + y³ + z³ = 3(a³ + b³). 

4) If x= w² - w - 2, evaluate x⁴+ 3x³ + 2x² -11 x -4.                                   3

5) If x= 2 - i √3, Find the value of k from the equation 2x⁴ - 5x³ - 3x² + 41x + k= 0.                                    -35

6) If cos a + i sin a, b= cos b+ I sin b, c= cos d + i sin d and a+ b+c= 0, prove that a²+ b²+ c²= 0.

7) If z= x + i y and (z- i)/(z + i) = i b, show that (x - 1/2)² + (y - 1/2)² = 1/2.

8) Prove that (a + bw + cw²) + (a + bw² + cw)³ = (2a- b - c)(2b - c - a)(2c - a- b) and 27abc, if a+ b+ c= 0.

9) If z= x + i y and arg{(z -1)/(z+ 1)} = π/4, Show that the locus of (x,y) is a circle.

10) If w be a Complex cube root of unity, find the simplified value of (a +bw + cw²)/(c + aw+ bw²) + (a +bw + cw²)/(b + cw+ aw²).                  -1

11) Show that the points 2+ 3i , 0 and 1/(-2 + 3i) are collinear.

12) Express a+ i b in the form pw + qw².                            (b/√3 - a)w + (-b/√3 - a)w² or (-b/√3 - a)w + (b/√3 - a)w²

13) solve: z² + z'= 0 (z= x+ i y).       0, -1, 1/2 ± √3 i/2.

14) If a²+ b²+ c²= 1 and b+ ic= (1+ a)z, then prove that (1+ i z)/(1- i z) = (a + i b)/(1+ c).

No comments:

Post a Comment