Find the equation of the circle which has its centre at the point (3, 4) and touches the straight line 5x + 12y – 1 = 0.
Find the equation of the circle which has its centre at the point (3, 4) and touches the straight line 5x + 12y – 1 = 0.

It is given that we need to find the equation of the circle with centre (3, 4) and touches the straight line 5x + 12y – 1 = 0.

RD Sharma Solutions for Class 11 Maths Chapter 24 – The Circle - image 7

RD Sharma Solutions for Class 11 Maths Chapter 24 – The Circle - image 8

Since, circle with centre (3, 4) and having a radius 62/13.

As, the equation of the circle with centre (p, q) and having radius ‘r’ is given by: (x – p)2 + (y – q)2 = r2

substituting the values in the equation, we get

    \[\begin{array}{*{35}{l}} {{\left( x\text{ }-\text{ }3 \right)}^{2}}~+\text{ }{{\left( y\text{ }-\text{ }4 \right)}^{2}}~=\text{ }{{\left( 62/13 \right)}^{2}}  \\ {{x}^{2}}~-\text{ }6x\text{ }+\text{ }9\text{ }+\text{ }{{y}^{2}}~-\text{ }8y\text{ }+\text{ }16\text{ }=\text{ }3844/169  \\ 169{{x}^{2}}~+\text{ }169{{y}^{2}}~-\text{ }1014x\text{ }\text{ }1352y\text{ }+\text{ }4225\text{ }=\text{ }3844  \\ 169{{x}^{2}}~+\text{ }169{{y}^{2}}~-\text{ }1014x\text{ }\text{ }1352y\text{ }+\text{ }381\text{ }=\text{ }0  \\ \end{array}\]

∴ The equation of the circle is 169x2 + 169y2 – 1014x – 1352y + 381 = 0.