AP EAMCET201922 Apr 2019Morning ShiftMathematicsCircleActual
The equation of a circle passing through the point ((2,8) ), touching the lines (4 x-3 y-24=0 ) and (4 x+3 y-42=0 ) and having the (x ) coordinate of its centre less than or equal to 8 is
Options
- A(x^2+y^2+2 x-8 y-8=0 )
- B(x^2+y^2-4 x-6 y-12=0 )
- C(x^2+y^2+4 x-10 y+4=0 )
- D(x^2+y^2-6 x-4 y-24=0 )
Correct answer
B. (x^2+y^2-4 x-6 y-12=0 )
Step-by-step solution
By the property of distance, ( aligned & | 4 h-3 k-24 5 |= | 4 h+3 k-42 5 | & = (h-2)^2+(k-8)^2 & 4 h-3 k-24= (4 h+3 k-42) & either 4 h-3 k-24=4 h+3 k-42 & 6 k=18 k=3 & or 4 h-3 k-24=-4 h-3 k+42 & 8 h=66 & h= 66 8 = 33 4 > 8 aligned ) Now, ((4 h-3 k-24)^2=25 [(h-2)^2+(k-8)^2 ] ) By solving this, we get, (h=2 ) ( ) Centre is ((2,3) ). Now, required circle is ( aligned & (x-2)^2+(y-3)^2 =25 & x^2+4-4 x+y^2+9-6 y =25 & x^2+y^2-4 x-6 x =12 aligned )