Coordinate GeometryClass 10 Mathematics NCERT Solutions
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Q1Exercise 7.1
Find the distance between the following pairs of points :
(i)
(ii)
(iii)
Solution
Formula:
The distance between two points and is given by the distance formula:
(i) Points and
Given:
Let and .
Solution:
Distance
Final Answer: The distance between the points and is units.
(ii) Points and
Given:
Let and .
Solution:
Distance
Final Answer: The distance between the points and is units.
(iii) Points and
Given:
Let and .
Solution:
Distance
Final Answer: The distance between the points and is units.
Q2Exercise 7.1
Find the distance between the points and . Can you now find the distance between the two towns A and B discussed in Section 7.2.
Solution
Part 1: Distance between and
Given:
Let the points be and .
So, and .
Formula:
The distance formula is .
For distance from the origin, this simplifies to .
Solution:
Distance OP
Final Answer (Part 1): The distance between the points and is 39 units.
Part 2: Distance between towns A and B
Given:
The problem in Section 7.2 describes town B located 36 km east and 15 km north of town A. If we consider town A to be at the origin of a coordinate system, then the coordinates of town B would be .
Solution:
The distance between town A and town B is the distance between the points and , which we calculated in Part 1.
Final Answer (Part 2): Yes, we can find the distance. The distance between the two towns A and B is 39 km.
Q3Exercise 7.1
Determine if the points and are collinear.
Solution
Given:
Let the points be , , and .
Condition for Collinearity:
Three points are collinear if the sum of the lengths of any two line segments among them is equal to the length of the remaining line segment. For example, if , the points are collinear.
Formula:
The distance formula: .
Solution:
We calculate the distances between each pair of points.
Distance AB:
Distance BC:
Distance AC:
Now, we check if the sum of any two distances equals the third.
Clearly, . Also, and .
Since the sum of the lengths of any two segments is not equal to the length of the third segment, the points do not lie on the same line.
Final Answer: The points and are not collinear.
Q4Exercise 7.1
Check whether , ( 6,4 ) and ( ) are the vertices of an isosceles triangle.
Solution
Given:
Let the vertices of the triangle be , , and .
Condition for an Isosceles Triangle:
A triangle is isosceles if at least two of its sides have equal length.
Formula:
The distance formula: .
Solution:
We calculate the lengths of the three sides of the triangle ABC.
Length of side AB:
Length of side BC:
Length of side AC:
Comparing the side lengths, we see that .
Since two sides of the triangle are equal, the triangle is an isosceles triangle.
Final Answer: Yes, the points , , and are the vertices of an isosceles triangle.
Q5Exercise 7.1
In a classroom, 4 friends are seated at the points A, B, C and D as shown in Fig. 7.8. Champa and Chameli walk into the class and after observing for a few minutes Champa asks Chameli, "Don't you think ABCD is a square?" Chameli disagrees. Using distance formula, find which of them is correct.
Solution
Given:
From the description of the seating arrangement, which can be represented on a coordinate plane, the positions of the four friends are:
, , , and .
To Determine:
Whether the quadrilateral ABCD formed by these points is a square.
Properties of a Square:
- All four sides are equal in length.
- Both diagonals are equal in length.
Formula:
The distance formula: .
Solution:
We calculate the lengths of the four sides and the two diagonals.
Side lengths:
units.
units.
units.
units.
Since , all four sides are equal.
Diagonal lengths:
units.
units.
Since , the diagonals are also equal.
Because all four sides are equal and both diagonals are equal, the quadrilateral ABCD is a square.
Conclusion:
Champa's observation that ABCD is a square is correct. Chameli disagrees, so Chameli is incorrect.
Final Answer: Champa is correct.
Q6Exercise 7.1
Name the type of quadrilateral formed, if any, by the following points, and give reasons for your answer:
(i)
(ii)
(iii)
Solution
(i) Points: A(-1,-2), B(1,0), C(-1,2), D(-3,0)
Solution:
We find the lengths of all four sides and the two diagonals.
All sides are equal: .
Now, we check the diagonals:
The diagonals are also equal: .
Reason: Since all four sides are equal and the diagonals are equal, the quadrilateral is a square.
Final Answer (i): Square.
(ii) Points: A(-3,5), B(3,1), C(0,3), D(-1,-4)
Solution:
We find the lengths of the sides.
No sides are equal. Let us check for collinear points. For points B, C, D:
, , .
. So, no three points are collinear.
Reason: The points form a quadrilateral with no special properties like equal sides or parallel sides (slopes are all different). It is a general quadrilateral.
Final Answer (ii): A general quadrilateral.
(iii) Points: A(4,5), B(7,6), C(4,3), D(1,2)
Solution:
We find the lengths of all four sides and the two diagonals.
Opposite sides are equal: and .
Now, we check the diagonals:
The diagonals are not equal: .
Reason: Since opposite sides are equal but the diagonals are not equal, the quadrilateral is a parallelogram.
Final Answer (iii): Parallelogram.
Q7Exercise 7.1
Find the point on the -axis which is equidistant from and .
Solution
Given:
Let the point on the x-axis be .
Let the given points be and .
The point P is equidistant from A and B, which means .
Condition:
Formula:
The square of the distance between and is .
Solution:
Setting :
Expanding the terms:
Subtract from both sides:
Rearranging the terms to solve for :
The point on the x-axis is .
Final Answer: The required point on the x-axis is .
Q8Exercise 7.1
Find the values of for which the distance between the points and is 10 units.
Solution
Given:
The points are and .
The distance between P and Q is 10 units, i.e., .
Formula:
The distance formula: .
So, .
Solution:
We are given , so .
Using the distance formula:
Now, solve for :
Taking the square root of both sides:
This gives two possible values for :
Case 1:
Case 2:
Final Answer: The possible values of are and .
Q9Exercise 7.1
If is equidistant from and , find the values of . Also find the distances QR and PR .
Solution
Part 1: Find the values of x
Given:
The point is equidistant from and .
This means , which implies .
Formula:
The square of the distance formula: .
Solution:
.
.
Setting :
or .
Final Answer (Part 1): The values of are and .
Part 2: Find the distances QR and PR
We need to find the distances for both values of .
Case 1:
The point R is .
Distance QR:
units.
Distance PR:
units.
Case 2:
The point R is .
Distance QR:
units.
Distance PR:
units.
Final Answer (Part 2):
When , and .
When , and .
Q10Exercise 7.1
Find a relation between and such that the point is equidistant from the point and .
Solution
Given:
Let the point be .
Let the given points be and .
The point P is equidistant from A and B, which means .
Condition:
Formula:
The square of the distance between and is .
Solution:
Setting :
Expanding the terms:
Combine like terms on each side:
Cancel and from both sides:
Move all terms to one side to form the relation:
Divide the entire equation by 4 to simplify:
Or, written in standard form:
Final Answer: The required relation between and is .
Q1Exercise 7.2
Find the coordinates of the point which divides the join of and in the ratio .
Solution
Given:
The line segment joins the points and .
The ratio of division is .
Let the point of division be .
Here, and .
Formula:
The section formula for a point that divides the line segment joining and in the ratio is:
Solution:
Calculating the x-coordinate:
Calculating the y-coordinate:
The coordinates of the point are .
Final Answer: The coordinates of the required point are .
Q2Exercise 7.2
Find the coordinates of the points of trisection of the line segment joining and .
Solution
Given:
Let the line segment be AB, with and .
The points of trisection are two points, let's call them P and Q, that divide the segment AB into three equal parts, i.e., .
Finding point P:
Point P divides the segment AB in the ratio .
Here, , , and .
Formula: Using the section formula:
,
Solution for P:
So, the coordinates of point P are .
Finding point Q:
Point Q divides the segment AB in the ratio . (Or, Q is the midpoint of PB).
Here, , , and .
Solution for Q:
So, the coordinates of point Q are .
Final Answer: The coordinates of the points of trisection are and .
Q3Exercise 7.2
To conduct Sports Day activities, in your rectangular shaped school ground ABCD, lines have been drawn with chalk powder at a distance of 1m each. 100 flower pots have been placed at a distance of 1 m from each other along AD, as shown in Fig. 7.12. Niharika runs th the distance AD on the 2nd line and posts a green flag. Preet runs th the distance AD on the eighth line and posts a red flag. What is the distance between both the flags? If Rashmi has to post a blue flag exactly halfway between the line segment joining the two flags, where should she post her flag?
Solution
Setting up the Coordinates:
Let's consider the ground as a coordinate plane where the lines are parallel to the y-axis and AD is along the y-axis.
The distance along AD is 100 m (since there are 100 pots at 1m distance).
Position of Niharika's Green Flag (G):
Niharika is on the 2nd line, so her x-coordinate is 2.
She runs th the distance AD, so her y-coordinate is .
Coordinates of the green flag G are .
Position of Preet's Red Flag (R):
Preet is on the 8th line, so her x-coordinate is 8.
She runs th the distance AD, so her y-coordinate is .
Coordinates of the red flag R are .
Part 1: Distance between the flags
Formula: Distance formula .
Solution:
Distance GR
Final Answer (Part 1): The distance between both the flags is m.
Part 2: Position of Rashmi's Blue Flag
Rashmi posts a blue flag exactly halfway between G and R. This is the midpoint of the line segment GR.
Formula: Midpoint formula .
Solution:
Let the position of the blue flag be B(x,y).
The coordinates for Rashmi's flag are .
This means she should post her flag on the 5th line at a distance of 22.5 m from the starting point along that line.
Final Answer (Part 2): Rashmi should post her flag on the 5th line at a distance of 22.5 m.
Q4Exercise 7.2
Find the ratio in which the line segment joining the points and is divided by .
Solution
Given:
Let the line segment be AB, with and .
Let the point of division be .
Let the ratio in which P divides AB be .
Method 1: Using the ratio
Formula: Section formula:
Solution:
Using the x-coordinate:
So, the ratio .
Verification using the y-coordinate:
. This matches the y-coordinate of P, so our ratio is correct.
Method 2: Using the ratio
Let the ratio be . The coordinates of the dividing point are:
We are given that .
Equating the x-coordinates:
The ratio is , which is .
Final Answer: The ratio is .
Q5Exercise 7.2
Find the ratio in which the line segment joining and is divided by the -axis. Also find the coordinates of the point of division.
Solution
Given:
The line segment joins and .
It is divided by the x-axis.
Understanding the problem:
Any point on the x-axis has its y-coordinate equal to 0. So, let the point of division be .
Let the ratio in which the x-axis divides the line segment AB be .
Formula:
Using the section formula, the coordinates of P are:
Here, and .
Part 1: Find the ratio
Solution:
We use the y-coordinate of point P, which is 0.
The ratio is .
Final Answer (Part 1): The ratio is .
Part 2: Find the coordinates of the point of division
Solution:
Now that we know the ratio is , we can find the x-coordinate of the point P.
The point of division is .
(Note: A ratio of 1:1 means the point of division is the midpoint.)
Final Answer (Part 2): The coordinates of the point of division are .
Q6Exercise 7.2
If and are the vertices of a parallelogram taken in order, find and .
Solution
Given:
Let the vertices of the parallelogram be , , , and taken in order.
Property of a Parallelogram:
The diagonals of a parallelogram bisect each other. This means the midpoint of diagonal AC is the same as the midpoint of diagonal BD.
Formula:
The midpoint of a line segment with endpoints and is .
Solution:
Midpoint of diagonal AC:
Midpoint of diagonal BD:
Since the midpoints are the same, :
Equating the x-coordinates:
Equating the y-coordinates:
Final Answer: The values are and .
Q7Exercise 7.2
Find the coordinates of a point A, where AB is the diameter of a circle whose centre is and is .
Solution
Given:
AB is the diameter of a circle.
The center of the circle is .
One endpoint of the diameter is .
Let the coordinates of the other endpoint A be .
Property of a Circle:
The center of a circle is the midpoint of its diameter.
Formula:
The midpoint formula: .
Here, the center C is the midpoint of AB.
Solution:
Using the midpoint formula for the x-coordinate:
Using the midpoint formula for the y-coordinate:
The coordinates of point A are .
Final Answer: The coordinates of point A are .
Q8Exercise 7.2
If A and B are and , respectively, find the coordinates of P such that and P lies on the line segment AB .
Solution
Given:
The points are and .
P is a point on the line segment AB.
The condition is .
To Find:
The coordinates of point P.
Finding the Ratio:
The condition can be written as .
Since P lies on AB, we have .
So, .
Now we can find the ratio in which P divides AB:
.
So, P divides the line segment AB in the ratio .
Formula:
Using the section formula:
Here, , , and .
Solution:
Calculating the x-coordinate of P:
Calculating the y-coordinate of P:
The coordinates of P are .
Final Answer: The coordinates of P are .
Q9Exercise 7.2
Find the coordinates of the points which divide the line segment joining and into four equal parts.
Solution
Given:
The line segment joins and .
We need to find three points, let's call them P, Q, and R, that divide AB into four equal parts, such that .
Strategy:
- Point Q is the midpoint of the entire segment AB.
- Point P is the midpoint of the segment AQ.
- Point R is the midpoint of the segment QB.
Formula:
The midpoint formula: .
Step 1: Find the coordinates of Q (midpoint of AB)
and
So, .
Step 2: Find the coordinates of P (midpoint of AQ)
and
So, .
Step 3: Find the coordinates of R (midpoint of QB)
and
So, .
Final Answer: The coordinates of the points that divide the line segment into four equal parts are , , and .
Q10Exercise 7.2
Find the area of a rhombus if its vertices are ( 3,0 ), ( 4,5 ), ( ) and ( ) taken in order. [Hint : Area of a rhombus (product of its diagonals)]
Solution
Given:
Let the vertices of the rhombus be , , , and .
To Find:
The area of the rhombus ABCD.
Formula:
Area of a rhombus , where and are the lengths of the diagonals.
The diagonals of the rhombus are AC and BD.
The distance formula is .
Solution:
Step 1: Calculate the length of diagonal AC
and
units.
Step 2: Calculate the length of diagonal BD
and
units.
Step 3: Calculate the area of the rhombus
Area
Area
Area
Area
Area square units.
Final Answer: The area of the rhombus is 24 square units.