Question 4
Check whether and are the vertices of an isosceles triangle.
Isosceles Triangle: A triangle is called isosceles if exactly two of its three sides are equal in length. To verify, we calculate the distance between each pair of points and check if at least two distances are equal.
Distance Formula: The distance between two points and is given by:
We will use the distance formula to find the length of each side of the triangle.
Step 1 — Calculate the length of side AB
Let's label the given points as A(), B(), and C(). We use the distance formula: .

Step 2 — Calculate the length of side BC
Now, let's find the distance between points B() and C(). We apply the distance formula again.
Step 3 — Calculate the length of side CA
Next, we find the distance between points C() and A(). We use the distance formula one more time.
Step 4 — Check if it is an isosceles triangle
We compare the lengths of the three sides we found. We have units, units, and units. An isosceles triangle has at least two sides of equal length. Here, we see that . Since two sides are equal, the triangle is isosceles.
Answer
Yes, the points , and are the vertices of an isosceles triangle.
More questions in Exercise 7.1
Find the distance between the following pairs of points :
(i) (ii) (iii)
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.
Determine if the points and are collinear.
Check whether and are the vertices of an isosceles triangle.
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.
Name the type of quadrilateral formed, if any, by the following points, and give reasons for your answer:
(i)
(ii)
(iii)
Find the point on the -axis which is equidistant from and .
Find the values of for which the distance between the points and is 10 units.
If Q(0, 1) is equidistant from P(5, –3) and R(x, 6), find the values of x. Also find the distances QR and PR.
Find a relation between x and y such that the point (x, y) is equidistant from the point (3, 6) and (–3, 4).