# FIND THE EQUATION OF THE LINE IN THE NEW POSITION

## About "Find the Equation of the Line in the New Position"

Find the Equation of the Line in the New Position :

Here we are going to see how to find the equation of the line in the new position if a line joining two points is rotated about the point in counter clockwise direction through given angle.

## Find the Equation of the Line in the New Position - Examples

Question 1 :

If the line joining two points A(2,0) and B(3,1) is rotated about A in anticlockwise direction through an angle of 15°, then find the equation of the line in new position.

Solution :

Let us represent the given information in a picture.

Let A (2, 0) and B (3, 1) be the given points.

Slope of PQ  = (y2 − y1) / (x2 − x1

=  (1 - 0) / (3 - 2)

= 1 ⇒ the angle of inclination of

the line AB = tan−1(1) = π/4  = 45

The slope of the line in new position is

m = tan(45 + 15)

Slope = tan(60) = (√3)

Equation of the straight line passing through (2, 0) and with the slope √3 is

y − 0  =  2 (x − √3)

2x − y + 2√3  =  0

Question 2 :

A ray of light coming from the point (1, 2) is reflected at a point A on the x-axis and it passes through the point (5,3). Find the co-ordinates of the point A.

Solution :

Let us represent the given details in a rough diagram.

The reflection point of A is A'. Its coordinate will be (1, -2).

Equation of A'B :

A'(1, -2)  B (5, 3)

(y - y1) / (y2 - y1)  =  (x - x1)/(x2 - x1)

(y - 3) / (3 + 2)  =  (x - 5)/(5 - 1)

(y - 3) / 5  =  (x - 5)/4

4 (y - 3)  =  5 (x - 5)

4y - 12  =  5x - 25

5x - 4y - 25 + 12  =  0

5x - 4y - 13  =  0

The required point (x, 0) lies on the line A'B

5x - 4(0) - 13  =  0

5x - 13  =  0

5x  =  13

x  =  13/5

Hence the required point is (13/5, 0).

After having gone through the stuff given above, we hope that the students would have understood "Find the Equation of the Line in the New Position".

Apart from the stuff given above, if you want to know more about "Find the Equation of the Line in the New Position".

If you have any feedback about our math content, please mail us :

v4formath@gmail.com

You can also visit the following web pages on different stuff in math.

WORD PROBLEMS

Word problems on simple equations

Word problems on linear equations

Algebra word problems

Word problems on trains

Area and perimeter word problems

Word problems on direct variation and inverse variation

Word problems on unit price

Word problems on unit rate

Word problems on comparing rates

Converting customary units word problems

Converting metric units word problems

Word problems on simple interest

Word problems on compound interest

Word problems on types of angles

Complementary and supplementary angles word problems

Double facts word problems

Trigonometry word problems

Percentage word problems

Profit and loss word problems

Markup and markdown word problems

Decimal word problems

Word problems on fractions

Word problems on mixed fractrions

One step equation word problems

Linear inequalities word problems

Ratio and proportion word problems

Time and work word problems

Word problems on sets and venn diagrams

Word problems on ages

Pythagorean theorem word problems

Percent of a number word problems

Word problems on constant speed

Word problems on average speed

Word problems on sum of the angles of a triangle is 180 degree

OTHER TOPICS

Profit and loss shortcuts

Percentage shortcuts

Times table shortcuts

Time, speed and distance shortcuts

Ratio and proportion shortcuts

Domain and range of rational functions

Domain and range of rational functions with holes

Graphing rational functions

Graphing rational functions with holes

Converting repeating decimals in to fractions

Decimal representation of rational numbers

Finding square root using long division

L.C.M method to solve time and work problems

Translating the word problems in to algebraic expressions

Remainder when 2 power 256 is divided by 17

Remainder when 17 power 23 is divided by 16

Sum of all three digit numbers divisible by 6

Sum of all three digit numbers divisible by 7

Sum of all three digit numbers divisible by 8

Sum of all three digit numbers formed using 1, 3, 4

Sum of all three four digit numbers formed with non zero digits

Sum of all three four digit numbers formed using 0, 1, 2, 3

Sum of all three four digit numbers formed using 1, 2, 5, 6