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## Friday, November 4, 2011

### SIMPLE PUZZLES

PUZZLE 15

A two-digit number, read from left to right, is 4.5 times as large as the same number read from right to left. What is the number?

PUZZLE 16

Some ducks are marching across a path. There's a duck in front of two ducks, there's a duck behind two ducks, and there's a duck in the middle of two ducks.

What's the least number of ducks that there could have been?

SOLUTIONS

PUZZLE 15 : 18 and 81

PUZZLE 16 : 3 Ducks.

## Wednesday, November 2, 2011

### LAPLACE TRANSFORM

Introduction:
•  The Laplace transform is named in honor of mathematician and astronomer Pierre-Simon Laplace, who used the transform in his work on probability theory.
• Like the Fourier transform, the Laplace transform is used for solving differential and integral equations.
• Laplace transform is a widely used integral transform.
• Laplace transform is just a shortcut for complex calculations.

Real Life Applications:
•    The Laplace transform turns a complicated nth order differential equation to a corresponding nth degree polynomial.

• In physics and engineering, it is used for analysis of linear time-invariant systems such as electrical circuits, harmonic oscillators, optical devices, and mechanical systems.
• The Laplace transform is one of the most important equations in digital signal processing and electronics.
•  In Nuclear physics, Laplace transform is used to get the correct form for radioactive decay.
• The Laplace transform reduces a linear differential equation to an algebraic equation, which can then be solved by the formal rules of algebra.FOR MORE APPLICATIONS CLICK HERE

## Friday, October 14, 2011

### Conformal Mapping

Geometric interpretation of a complex function.

If D is the domain of real-valued functions and u(x,y) and v(x,y) then the system of equations u = u(x,y) and v = v(x,y) describes a transformation (or mapping) from the x y - plane into the u v -plane, also called the w-plane.

Therefore, we consider the function w= f(z) = u(x,y) + i v (x,y)
to be a transformation (or mapping) from the set D in the z-plane onto the range R in the w-plane.
Conformal Mapping:

A function f: C → C is conformal at a point z₀ if and only if it is holomorphic and its derivative is everywhere non-zero on C.

i.e., if f is analytic at z₀ and f’(z₀) ≠ 0

Isogonal Mapping:

An isogonal mapping is a transformation w = f (z) that preserves the magnitudes of local angles, but not their orientation.

Standard Transformations:

• Translation

- Maps of the form z → z + k, where k є C

• Magnification and rotation

- Maps of the form z → k z , where k є C
•  Inversion

- Maps of the form z → 1 / z

### Transformation w = a z

Let w = a z, where a ≠ 0

If a = │a│ e^(i α) and, z = │z │ e^(i θ), then

w = │a│ │z│ e^i(θ + α )

The image of z is obtained by rotating the vector z through the angle α and magnifying or contracting the length of z by the factor │a│.

Thus the transformation w = a z is referred to as a rotation or magnification.

﻿﻿﻿﻿
Example 1:

Find the image of the region y > 1 under the map w = ( 1 – i ) z

Solution:

Let w = u + i v ; z = x + i y

Given w = ( 1 – i ) z

i.e., z = 1/2 ( 1 + i) w      [ since ( 1 – i ) ( 1 + i) = 2]

i.e., x + i y = 1/2 ( 1 + i) (u + i v )

i.e., x = (u- v )/2 ; y = (u+v)/2

Hence the region y >1 is mapped on the region u + v > 2 in w –plane.

Example 2 :

Determine the region R of the w plane into which the triangular region D enclosed by the lines
x = 0, y = 0, x + y = 3 is transformed under the transformation w = 2z.

Solution:
Let w = u +i v; z = x + i y

Given, w =2 z

i.e., u +i v = 2 (x + i y)

i.e., u = 2 x ; v = 2 y

When x = 0, u = 0

The line x = 0 is transformed into the line u = 0 in the w – plane.

When y = 0, v = 0

The line y = 0 is transformed into the line v = 0 in the w – plane.

When x + y = 3 , we get

u/2 + v/2 = 3

i.e., u + v = 6

The line x + y = 3 is transformed into the line u + v = 6 in the w – plane.

## Wednesday, August 10, 2011

### CIRCLE AND ITS RELATED TERMS

Circle is the set of all points in a plane that are equidistant from a given point in the plane known as the center of the circle.

Chord -
is a segment whose endpoints lie on a circle

Secant -
is a line that intersects the circle at two points

Diameter is the longest secant in a circle.

Tangent - is a line in the plane of the circle that intersects the circle at exactly one point
Sector -The part of a circle enclosed by two radii  of a circle and an arc.
The cut piece of pizza is minor sector and the remaining is the major sector.

Segment -part of a circle bounded by a chord and an arc

Semi-circle -
is an arc whose endpoints are endpoints of a diameter

## Tuesday, August 9, 2011

### Applications of Trigonometry in Real life

• Trigonometry is commonly used in finding the height of towers and mountains.

• It is used in navigation to find the distance of the shore from a point in the sea.

• It is used in oceanography in calculating the height of tides in oceans

• It is used in finding the distance between celestial bodies

• The sine and cosine functions are fundamental to the theory of periodic functions such as those that describe sound and light waves.

• Architects use trigonometry  to calculate structural load, roof slopes, ground surfaces and many other aspects, including sun shading and light angles

## Friday, March 25, 2011

### THE NUMBER 13

Two interesting facts about the number 13:

(i)  (1 / 13 )   =     0.076923076923076923076923...
(rational periodic infinite decimal)

On multiplying the periodic number 76923 by successive multiples of 13, the following curious numerical pattern is obtained.
76923 * 013 = 0999999
76923 * 026 = 1999998
76923 * 039 = 2999997
76923 * 052 = 3999996
76923 * 065 = 4999995
76923 * 078 = 5999994
76923 * 091 = 6999993
76923 * 104 = 7999992
76923 * 117 = 8999991
76923 * 130 = 9999990

(ii) The numerical pattern abcabc is divisible by 13.

## Friday, February 4, 2011

### An interesting fact about the powers of 10

There seems to be only 11 powers of ten that are products of 2 integers without any zero digits.

10 ^ 0     =                      1 * 1
10 ^ 1     =                      2 * 5
10 ^ 2     =                      4 * 25
10 ^ 3     =                      8 * 125
10 ^ 4     =                      6 * 625
10 ^ 5     =                    32 * 3125
10 ^ 6     =                    64 * 15625
10 ^ 7     =                  128 * 78125
10 ^ 9     =                  512 * 1953125
10 ^ 18   =             262144 * 3814697265625
10 ^ 33   =      8589934592 * 116415321826934814453125

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