1. Use the Circle with Centre through Point tool to create a circle centre A and radius AC.[br]2. Draw a diameter of the circle to meet the circle where it crosses BC.[br]3. Draw a line from C to meet where the diameter meets the circle on the other side.[br]4. Use the Angle tool to check that the angle at C is 90[math]^\circ[/math].

1. Draw a circle centred at B so that its radius goes past the line.[br]2. Use the Intersect tool to mark the 2 intersections of this circle with the line.[br]3. Draw 2 circles with their centres at these points of intersection and passing through B.[br]4. Use the Intersect tool to mark the point of intersection of these 2 circles below the line.[br]5. Draw a line segment between B and this point of intersection.[br]6. Use the Angle tool to check the size of the angle between this line and the original line.