Find the coordinates of a point A, where AB is the diameter of a circle whose centre is (2, – 3) and B is (1, 4).
Let the coordinates of point A be (x, y).
Mid-point of AB is (2, −3), which is the center of the circle.
\(\therefore\,(2,-3)=(\frac{x+1}{2},\frac{y+4}{2})\)
\(\Rightarrow \, \frac{x+1}{2}=2\, and\,\frac{y+4}{2}=-3\)
\(\Rightarrow \,x+1=4\,and\,y+4=-6\)
\(\Rightarrow \,x=3\,and\,y=-10\)
Therefore, the coordinates of A are (3,-10)
Determine if the points (1, 5), (2, 3) and (– 2, – 11) are collinear
In a classroom, 4 friends are seated at points A, B, C and D. 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 the distance formula, find which of them is correct.
| Case No. | Lens | Focal Length | Object Distance |
|---|---|---|---|
| 1 | \(A\) | 50 cm | 25 cm |
| 2 | B | 20 cm | 60 cm |
| 3 | C | 15 cm | 30 cm |