A trefoil is a common motif found in gothic architect. In it’s most basic form it consists of three circular elements in the shape of a triangle. This how to describes the construction of a trefoil inside a circle, and is useful when setting out tracery with defined constraints.

### Method Of Construction

- Draw a centre line and circle
- Mark the points for the equilateral triangle
- Draw an equilateral triangle
- Find the centre points for lower lobes
- Draw the circles of the trefoil

### Draw A Centre Line And Circle

Draw a vertical centre line *a-b*, and on that line draw a circle with a radius *c* that you wish to fit the trefoil inside.

### Mark Points For Equilateral Triangle

Without adjusting the compass, place it’s point at *d* where the previously drawn circle intersects line *a-b*. Draw two arcs *e* and *f* at the intersection points with the original circle.

### Draw An Equilateral Triangle

Draw an equilateral triangle from points *e*, *f*, and point *g*. Point *g* is at the intersection of vertical line *a-b* and the original circle.

### Find The Centre Points For The Lower Lobes

Using point *e* and the centre point of the original circle, construct line *e-i*. Using point *f* and the centre point of the original circle, construct line *f-h*. Points *h* and and *i* are the centre points of the lower lobes.

### Draw The Circles Of The Trefoil

Place the point of the compass at point *h* and adjust the radius so that it touches the centre point of the original circle. Draw three circles at points *h*, *i*, and *j* with this radius. The resultant three circles describe a trefoil drawn in a circle with a given radius.

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