Question
The equation of the circle, which touches the line y=5 and passes through (-1,2) and (1,2) is
BITSAT
Mathematics
Circle
2021
BITSAT 2021
BITSAT Mathematics Question (2021) — Solution
Options
- A. 9 x^ 2 +9 y^ 2 -60 y+75=0
- B. 9 x^ 2 +9 y^ 2 -60 x-75=0
- C. 9 x^ 2 +9 y^ 2 +60 y-75=0
- D. 9 x^ 2 +9 y^ 2 +60 x+75=0
Answer
A. 9 x^ 2 +9 y^ 2 -60 y+75=0
Step-by-step solution
The centre of the circle is on the perpendicular bisector of the line joining (-1,2) and (1,2), which is the y-axis. The ordinate of the centre is given by array l (5-y)^ 2 =1+(y-2)^ 2 \\ y= 10 3 array Hence, eq. of the circle is: array l x^ 2 + (y- 10 3 )^ 2 = ( 5 3 )^ 2 \\ 9 x^ 2 +9 y^ 2 -60 y+75=0 array
Related: Mathematics — Circle · All PYQ Banks