# Space, shape and measurement: Use the Cartesian co-ordinate system to derive and apply equations ### Subject outcome

Subject outcome 3.1: Use the Cartesian co-ordinate system to derive and apply equations ### Learning outcomes

• Use the Cartesian coordinate system to derive and apply the equation of a circle (any centre).
• Use the Cartesian coordinate system to derive and apply the equation of a tangent to a circle given a point on the circle. Note that:
• Straight lines to be written in the following forms only: $\scriptsize y=mx+c$, $\scriptsize y-{{y}_{1}}=m(x-{{x}_{1}})$ and/or $\scriptsize ax+by+c=0$ (general form).
• Learners are expected to know and be able to use as an axiom ‘the tangent to a circle is perpendicular to the radius drawn to the point of contact.’ ### Unit 1 outcomes

By the end of this unit you will be able to:

• Find the equation of a circle centred at the origin.
• Find the equation of a circle with centre $\scriptsize (a,b)$.
• Write the equation of the circle in standard form. ### Unit 2 outcomes

By the end of this unit you will be able to:

• Find the gradient of a tangent to a circle using analytical geometry.
• Find the equation of a tangent to the circle using analytical geometry.
• Find the equation of a tangent to a circle at the point of contact with the radius. 