Questions in circle

Select	Question
	The equation of director circle of the circle ${{x}^{2}}+{{y}^{2}}={{a}^{2}},$ is
	If O is the origin and OP, OQ are tangents to the circle ${{x}^{2}}+{{y}^{2}}+2gx+2fy+c=0$ , the circumcentre of the triangle $OPQ$ is
	The equation of circle which touches the axes of coordinates and the line $\frac{x}{3}+\frac{y}{4}=1$ and whose centre lies in the first quadrant is ${{x}^{2}}+{{y}^{2}}-2cx-2cy+{{c}^{2}}=0$ , where c is
	The number of tangents which can be drawn from the point (–1,2) to the circle ${{x}^{2}}+{{y}^{2}}+2x-4y+4=0$ is
	The number of tangents that can be drawn from (0, 0) to the circle ${{x}^{2}}+{{y}^{2}}+2x+6y-15=0$ is
	At which point on y-axis the line $x=0$ is a tangent to circle ${{x}^{2}}+{{y}^{2}}-2x-6y+9=0$
	The number of common tangents to the circles ${{x}^{2}}+{{y}^{2}}-4x-6y-12=0$ and${{x}^{2}}+{{y}^{2}}+6x+18y+26=0$ is
	If the straight line $y=mx+c$ touches the circle ${{x}^{2}}+{{y}^{2}}-4y=0$ , then the value of c will be
	The area of triangle formed by the tangent, normal drawn at $(1,\sqrt{3})$ to the circle ${{x}^{2}}+{{y}^{2}}=4$ and positive x-axis, is
	Line $y=x+a\sqrt{2}$ is a tangent to the circle ${{x}^{2}}+{{y}^{2}}={{a}^{2}}$ at