Two circles have radii r1 r_1\,r1 and r2r_2r2, and the distance between their centres is ddd.
State the condition for the circles to touch externally.
State the condition for the circles to touch internally.
76 exam-style questions on WJEC A Level Maths 1.3 Coordinate geometry in the (x, y) plane, covering 1.3.1 Coordinate geometry in the (x, y) plane, 1.3.2 Coordinate geometry in the (x, y) plane, 1.3.3 Coordinate geometry in the (x, y) plane, and 1.3.4 Coordinate geometry in the (x, y) plane. Each one has a worked solution and a mark scheme showing where the marks go.