1.

The area of the circle centred at (1,2) and passing through (4,6) isA. `5pi` sq unitB. `5pi` sq unitC. `5pi` sq unitD. None of the above

Answer» Correct Answer - D
The equation of a circle centred at (1,2) and passing through (4,6) is
`(x-1)^(2)+(y-2)^(2)=(4-1)^(2)+(6-2)^(2)`
`Rightarrow x^(2)+y^(2)-2x-4y+1+4=9+16`
`Rightarrow x^(2)+y^(2)-2x-4y-20=0`
Now, radius `=sqrt((-1)^(2)+(-2)^(2)+20)`
`=sqrt(1+4+20)=5`
`therefore ` Area of circle `=pir^(2)`
`=25pi"sq unit"`


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