The tangent to a circle is a special case of the secant when the two endpoints of corresponding chord coincide

In the figure, $O$ is the centre of the circle and $x^2+y^2=25$ is the equation of the circle. What is the radius of the circle?

The perpendicular drawn from the centre of a circle to a chord bisect the chord.

In the given figure $TP$ and $TQ$ are two tangents to the circle with centre $O$, touching at $A$ and $C$ respectively. If $\angle BCQ=55°$ and $\angle BAP=60°$, find $\angle OBA$ and $\angle OBC$

What is the circumference of the largest circle which can be inscribed in a square of side $14 cm$? ($\mathrm{\pi }=\frac{22}{7}$)

In the figure, $O$ is the centre of the circle and $x^2+y^2=25$ is the equation of the circle. Write the equation of the circle whose centre is at origin and the radius is $3$.

In the given figure $TP \& TQ$ are two tangents to the circle with centre $O$, touching at $A \& C$ respectively. If $\angle BCQ=55° \& \angle BAP=60°$, find $\angle ATC$ in degrees.